Planta

Cannabis sativa prenyltransferase 4 (CsPT4) and prenyltransferase 1 (CsPT1) have been shown to catalyze the step in the cannabinoid biosynthetic pathway that generates cannabigerolic acid (CBGA), the substrate for the end-point enzymes that generate cannabidiolic acid (CBDA) and tetrahydrocannabinolic acid (THCA). Prior studies from our lab suggest that CBGA production rate-limits the pathway. There is a lack of understanding concerning how important cannabinoid biosynthetic genes are regulated as cannabinoid synthesis increases during female flower development. Both CsPT genes were shown to be highly expressed in flowers. The genes were also found to be present in leaves and roots. GUS staining also detected the promoter activities in leaves of seedlings, and the promoter activities were drastically stronger in the section of the sugar leaves where glandular trichomes are formed. In silico analysis of the two CsPT genes revealed several hormone and transcription factor responsive elements. Dual luciferase assays were conducted to determine whether a hormone could alter the promoter activities of CsPT1 and CsPT4. The results showed that CsPT4 pro was activated following treatment from salicylic acid (SA), gibberellic acid (GA), ethylene, ABA, and cytokinin, while the CsPT1 promoter was activated following SA, ethylene, ABA, and auxin treatment. In parallel studies, a correlation was observed between multiple cannabinoid biosynthetic pathway genes and SA application to the cannabis growing medium, along with a correlation between MeSA floral application and an increase in cannabinoid content. The results from all aspects of this study demonstrated an interaction between certain hormones and cannabinoid synthesis.

Among candidate genes underlying the control components of apomixis, APOLLO is known for its strong linkage to apomeiosis in the genus Boechera. The gene has "apo-alleles", which are characterized by a set of linked apomixis-specific polymorphisms, and "sex-alleles". All apomictic{square}Boechera genotypes are heterozygous for the apo/sex-alleles, while all sexual genotypes are homozygous for sex-alleles. In this study, native and synthetic APOLLO promoters were characterized by detecting the expression level of the {beta}-glucuronidase (GUS) gene in Arabidopsis. Comparing various flower developmental stages in transgenic lines containing different constructs with 2 kb native transgenic lines revealed that changes to the APOLLO promoter causes shifts in tissue- and developmental-stage specificity of GUS expression. Importantly, several apomixis-specific polymorphisms in the 5UTR change the timing and location of GUS activity from somatic to reproductive tissues. These synthetic data simulate a plausible evolutionary process whereby apomixis-specific gene activity can be achieved.

The sterile pollen technique, which involves applying X-ray irradiated pollen to female plants, has shown promising results in reducing seed production in dioecious Palmer amaranth (Amaranthus palmeri S. Wats.). However, field-scale implementation of this method requires a carrier for pollen delivery, as applying pure pollen on a large scale is not practical. Additionally, variability in flowering time within and among individual plants may impact the techniques effectiveness. Mass pollination may also lead to a female-biased sex ratio in the progeny, a phenomenon known as certation. Therefore, in this study, we aimed to: (1) identify a suitable dry (inert) diluent and the most effective pollen-to-diluent ratio for large-scale application, and (2) determine the most effective combination of initiation time, frequency, and number of sterile pollen applications, and 3) test for evidence of certation in A. palmeri. Plants were grown in the greenhouse in summer 2021. Sterilized pollen irradiated at 300 Gy was mixed with talc or wheat powder flour, respectively, at six v/v ratios (pollen%/powder%) of 0/100 (powder alone), 5/95, 10/90, 25/75, 50/50, or 100/0 (pure irradiated pollen). An equal amount of the pollen-diluent powder mixture was then brushed onto the standardized lengths of inflorescence of receptive female plants. Flower and seed number on each inflorescence was counted and used to calculate seed set in each treatment. The findings showed that a minimum of 25% irradiated pollen in the mixture, either with talc powder or wheat flour, can effectively reduce seed set in A. palmeri. Building on this, a second round of greenhouse experiments was conducted in fall 2021, where female plants were pollinated with a 25% irradiated pollen and talc powder mixture using a powder duster. Pollination treatments were initiated at different times after anthesis (7, 14, and 21 days), and the number of applications varied (once, twice, or three times) with intervals of one, two, or three weeks between applications. The greatest reduction in seed output was achieved when sterile pollen application began seven days after anthesis and was repeated three times at 7-day intervals. Evidence of certation was also observed in A. palmeri, with the progeny of mass-pollinated females showing a higher female ratio (58%) compared to the open-pollinated population (47%). Mass pollination also led to a slight, though not statistically significant, reduction in plant size traits such as height and number of branches, providing an additional potential benefit of the sterile pollen technique.

Sexual plasticity is a phenomenon wherein organisms possess the ability to alter their phenotypic sex in response to environmental and physiological stimuli, without modifying their sex chromosomes. Cannabis sativa L., a medically valuable plant species, exhibits sexual plasticity when subjected to specific chemicals that influence ethylene biosynthesis and signaling. Nevertheless, the precise contribution of ethylene-related genes (ERGs) to sexual plasticity in cannabis remains unexplored. The current study employed Arabidopsis thaliana L. as a model organism to conduct gene orthology analysis and reconstruct the Yang Cycle, ethylene biosynthesis, and ethylene signaling pathways in C. sativa. Additionally, two transcriptomic datasets comprising male, female, and chemically induced male flowers were examined to identify expression patterns in ERGs associated with sexual determination and sexual plasticity. These ERGs involved in sexual plasticity were categorized into two distinct expression patterns: floral organ concordant (FOC) and unique (uERG). Furthermore, a third expression pattern, termed karyotype concordant (KC) expression, was proposed, which plays a role in sex determination. The study revealed that CsERGs associated with sexual plasticity are dispersed throughout the genome and are not limited to the sex chromosomes, indicating a widespread regulation of sexual plasticity in C. sativa. Key MessagePresented here are model Yang cycle, ethylene biosynthesis and signaling pathways in Cannabis sativa. C. sativa floral transcriptomes were used to predict putative ethylene-related genes involved in sexual plasticity in the species.

Genome editing is now available for many crops. It has increased our ability to study gene function and has changed the field of plant transgenesis. Nevertheless, the ability to regenerate plants from cell culture remains a limiting factor for many crops, and even for species with a good regeneration potential, some accessions remain recalcitrant. The physiological state of plant cells is involved in the process of plant growth and development and is closely linked to the network involving MAP-kinase signaling pathway. Some of the defense genes activated during the cellular repair process of transgenesis show high homologies with mammalian defense genes. We thus compared the percentage of transgenic plants obtained by CRISPR-Cas9 mutation in four genes involved in sugar and acid metabolism after supplementation with different mammalian growth factors and cytokines in six tomato accessions presenting a range of regeneration levels. We demonstrated, through three years of transgenesis experiments, that the use of mammalian growth factors during transgenesis improved regeneration rate of recalcitrant tomato accessions. We demonstrated that using cytokines not only improved transformation of difficult-to-transform accessions but also the production rate of stable secondary lines. Summary statementSupplementation of transformation medium with mammalian growth-regulating factors enhanced regeneration of tomato recalcitrant genotypes

MicroRNAs are critical components of the multi-dimensional regulatory networks in eukaryotic systems. They regulate a spectrum of developmental and metabolic processes in both plants and animals. Thus, it is quite apparent that the transcription, processing as well as activity of the miRNAs themselves is very dynamically regulated. One of the most important and universally implicated signalling molecule is [Ca2+]cyt. It is known to regulate a plethora of developmental and metabolic processes in both plants and animals, however their impact on the regulation of miRNA expression is relatively less explored. The current study employed a combination of internal and external calcium channel inhibitors, to establish that [Ca2+]cyt signatures actively regulate miRNA expression in rice. Involvement of [Ca2+]cyt in regulation of miRNA expression was further confirmed by treatment with calcimycin, the calcium ionophore. Modulation of the cytosolic calcium levels was also found to regulate the drought responsive expression as well as ABA mediated response of miRNA genes in rice seedlings. The study further establishes the role of calmodulins and Calmodulin-binding Transcription Activators (CAMTAs) as important components of the signal transduction schema that regulates miRNA expression. Yeast-one-hybrid assay established that OsCAMTA4 & 6 are involved in the transcriptional regulation of miR156a and miR167h. Thus, the study was able to clearly establish that [Ca2+]cyt is actively involved in regulating expression of miRNA genes both under control and stress conditions.

Cannabis is a multi-billion dollar industry reliant on unpollinated genetically female (XX) plants, as pollination reduces cannabinoid yields and flower quality. The mechanism behind the sexual expression of C. sativa is unclear. This study examines the sexual characteristics of homo- and hetero-gametic triploid cannabis plants (XX(X/Y)) to understand the role of the Y chromosome in cannabis sex determination. Heterogametic triploids were produced by crossing a male diploid C. sativa cv. Durban Poison (2n = 2x = 18 + XY) with a tetraploid female C. sativa cv. Higher Education (2n = 4x = 36 + XXXX) confirmed by flow cytometry and PCR. Measurements include fresh and dry plant weight, dry flower weight, seed counts, seed weights, and cannabinoids quantified using liquid chromatography. Results showed 44.4% of plants were XXY (n = 8), with 75% presenting a monoecious phenotype (n = 6). Of these, 50% produced predominately male flowers (n = 3), while the rest produced predominately female flowers. Plants with predominately female flowers had higher yields and cannabinoids compared to predominantly male plants. XXX genotypes outperformed XXY in several metrics. This study enhances our understanding of C. sativa sex determination and offers insight into breeding and cultivation strategies utilizing triploid cannabis.

Root hair cells, which are instrumental in water and nutrient uptake, grow polarly from the epidermal cell layer of the root. Furthermore, plants growing in challenging climates and complex soil environments acclimatize their root hair phenotypes, either by altering root hair length or density. Toxic metal stress is one of the major environmental stresses faced by plant roots. In this study, we demonstrate that toxic metals, such as chromium and arsenite, increase root hair density as an adaptive response. Using the model plant Arabidopsis thaliana and other crops plants, like Zea mays and Triticum aestivum, we further discovered that increased root hair density is caused by shorter epidermal cell length rather than alteration of epidermal cell fate. This study highlights the adaptive cellular and anatomical features of roots during toxic metal stress in evolutionary diverse plant species.

Eggplant (Solanum melongena L.) is one of the most important vegetables grown and consumed in the Philippines; hence, continuous breeding programs are vital to maintain the supply of this economically important crop. This study demonstrates the first successful Agrobacterium-mediated genetic transformation and plant regeneration of a Philippine eggplant cultivar, PH 11424 also known as Mistisa. Cotyledons from two-week old seedlings were used as explants, which were transformed with disarmed Agrobacterium tumefaciens strain LBA4404 harboring a binary vector for CRISPR/Cas9 expression and hygromycin phosphotransferase (HPT), an antibiotic selection marker. Growth of shoot primordia from the agro-infected explants was observed during selective culture with 7.5 ppm hygromycin, which indicated an initial transformation success. The putatively transformed shoot primordia were then transferred to an elongation medium. The elongated and hygromycin-resistant shoots were allowed to develop roots in hormone-free medium supplemented with hygromycin, and subsequently acclimatized under greenhouse conditions. The entire process took at least 5 - 6 months. Of the total 585 agro-infected explants, the regeneration efficiency of rooted shoots was 5.1%. Successful transformation was confirmed by polymerase chain reaction (PCR) amplification of Cas9. Acclimatized plants tested positive for the transgene. The transgenic eggplants successfully reached maturity, flowered, and set seed. These results demonstrate a working Agrobacterium-mediated transformation and plant regeneration protocols using cotyledons as explants in a Philippine eggplant genotype. These biotechnology tools are critical for the successful application of genetic engineering (GE) and new breeding techniques (NBTs) in eggplant crop improvement.

Hormesis refers to the adaptive mechanism of organisms in response to environmental challenges where a lower dose of a toxic compound induce an improvement in functionality and overall development and a higher dose endangers even the existence of the organism. The recent developments in hormetic studies are of paramount importance in plant research as they help in risk assessment of environmental contaminants, protect the vegetation against pollution, and improve crop productivity. As one of the most toxic contaminants, cadmium is considered to have detrimental effects on the growth and development of plants. However, recent studies have revealed the beneficial effects of cadmium in plants at low levels of exposure however the exact mechanism behind this phenomenon is poorly deciphered. In this study, we have focused on observing the response of tomato seedlings under different concentrations of cadmium. The morphological, biochemical, and histochemical characterization of these seedlings under low cadmium exposure has confirmed their hormetic effects. The differential gene expression by transcriptomic profiling in low cadmium showed that, apart from genes involved in oxidoreductase activity, and signaling, several lncRNAs, also differentially expressed. The lncRNAs are known to regulate gene expression on the chromatin level and post-transcriptional regulation. First time we are reporting the expression of lncRNAs in hormesis as important factor for enhanced growth. In-silico analysis revealed the functions of lncRNAs, involving the prediction of cis-targets, mi-RNA precursors, and their targets. Two miRNAs; sly-MIR396a and sly-MIR1063g were seen to have a direct role in improving the growth of plants treated with low cadmium provided an insight into the molecular mechanisms of their role in cadmium hormesis. These findings provided important understanding of the molecular basis of the hormetic phenomenon which can pave a path for generating crops with improved agronomic characteristics. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=149 SRC="FIGDIR/small/663119v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@8de5b0org.highwire.dtl.DTLVardef@1e2ad13org.highwire.dtl.DTLVardef@d0f7e2org.highwire.dtl.DTLVardef@14238b3_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LILow cadmium exposure on Solanum lycopersicum seedlings showed more promising outcomes in terms of growth and development. C_LIO_LIThe plants exposed to 1{micro}M Cd treatment continued to exhibit superior growth responses despite removing the cadmium from the media after 5 days of treatment. C_LIO_LIThe GO analysis of Differentially Expressed Genes (DEGs) suggested several lncRNAs differentially expressed in 1 {micro}M Cd condition. C_LIO_LIDifferentially expressed LncRNAs Solyc01g006780.4 and Solyc12g019150.1 generated the miRNAs, sly-MIR396a and sly-MIR1063g respectively. C_LIO_LIUpregulation of sly-MIR396a and sly-MIR1063g resulted in the downregulation of GRF12 and NET4B-like proteins respectively leading to increased growth of tomato plants. C_LI

Maize is a staple food all over the world. Models for climate change suggest that, in the future, cloud formation might be reduced in the tropics increasing the exposure to Ultraviolet-B (UV-B) radiation, a DNA-damaging agent. UV-B (290 to 320 nm) has been shown to affect yield in maize. In this project we have determined the differences in DNA repair efficiencies between U.S. inbred lines B73 and Mo17, and Central American purple landraces from Guatemala and Costa Rica. Our results from single cell electrophoresis experiments (Comet Assay) suggest that the landrace Pujagua Santa Cruz (P1, Costa Rican) was resistant to damage caused by the radiomimetic agent zeocin (24h/100 micrograms per mL), while landrace Pujagua La Cruz (P2, Costa Rican) was able to repair DNA damage after one hour. On the other hand, line Mo17 (Missouri, USA) was unable to repair the damage, while B73 (Iowa, USA) and the landraces Jocopilas (Guatemalan), Orotina Congo (Costa Rican) and Talamanca (Costa Rican) were partially able to repair DNA damage. High Resolution Melting (HRM) curve analysis of putative homologous DNA repair gene ZeaATM1 showed that both P1 and P2 had differences in the melting temperatures for this gene compared to B73 and Mo17, while P1 showed additional differences in ZeaSOG1, ZeaRAD51 and ZeaBRCA1, suggesting that in this landrace the presence of polymorphisms may be common among key genes for this pathway. Taken together our results suggest that key adaptive differences in DNA repair efficiencies exist between inbred lines and landraces of maize and that some Central America landraces could be used as a valuable pool of alleles for plant breeding aiming to increase tolerance to radiation.

Allicin is a defence substance produced by garlic cells upon injury. It is a thiosulfinate showing redox-activity and a broad range of antimicrobial and biocidal activity. It is known that allicin efficiently oxidizes thiol-groups and it has been described as a redox toxin. In order to learn more about the effect of allicin on plants we used pure synthetized allicin, and investigated cytoplasmic streaming in sterile filaments of Tradescantia fluminensis, organelle movement using transgenic Arabidopsis with organelle-specifics GFP-tags, and effects on actin and tubulin in the cytoskeleton using GFP-tagged lines. Auxin distribution in roots was investigated using PIN1:GFP, PIN3:GFP, DR5:GFP and DII-VENUS Arabidopsis reporter lines. Allicin inhibited cytoplasmic streaming in T. fluminensis and organelle movement of peroxisomes and the Golgi apparatus in a concentration-dependent manner, inhibited root growth and destroyed the correct root tip distribution of auxin. We speculate that the cytoskeleton can be a primary "receptor" for allicins oxidizing properties and as a consequence cytoskeleton-dependent cellular processes are disrupted.

Inducible systems for transgene expression activated by a chemical inducer or an inducer of non-plant origin are desirable tools for both basic plant research and biotechnology. Although, the technology has been widely exploited in model plants, it has not been optimised for use with the major monocotyledonous crop species, namely rice. We have adapted the dexamethasone-inducible pOp6/LhGR system for rice and shown that it is fast, sensitive and tightly regulated, with high levels of induction that remain stable over several generations. Most importantly, we have shown that the system does not cause negative growth defects in vitro or in soil grown plants. Interestingly in the process of testing, we found that another steroid, triamcinolone acetonide, is a more potent inducer in rice than dexamethasone. We present serious considerations for the construct design to avoid undesirable effects caused by the system in plants, leakiness and possible silencing, as well as simple steps how to maximize translation efficiency of a gene of interest. Finally, we compare the performance of the pOp6/LhGR system with other chemically inducible systems tested in rice in terms of the properties of an ideal inducible system. Significance statementThe non-monocot codon-optimized version of the dexamethasone inducible pOp6/LhGR system does not cause severe developmental perturbations in rice plants.

Chloroplast perturbations activate retrograde signalling pathways causing dynamic changes of gene expression. Besides transcriptional control of gene expression different classes of small non-coding RNAs (sRNAs) act in gene expression control, but comprehensive analyses regarding their role in retrograde signalling is lacking. We performed sRNA profiling in response to norflurazon (NF) that provokes retrograde signals in A. thaliana wild type and the two retrograde signalling mutants gun1 and gun5. The RNA samples were also used for mRNA and long non-coding RNA (lncRNA) profiling to link altered sRNA levels to changes of their cognate target RNAs. We identified 122 sRNAs from all known sRNA classes that were responsive to NF in wild type. Strikingly, 140 and 213 sRNAs were found to be differentially regulated in both mutants indicating a retrograde control of these sRNAs. Concomitant with the changes in sRNA expression we detected about 1500 differentially expressed mRNAs in the NF treated wild type and around 900 and 1400 mRNAs that were differentially regulated in the gun1 and gun5 mutant with a high proportion (~30%) of genes encoding plastid proteins. Furthermore, around 20% of predicted miRNA targets code for plastid localised proteins. The analyses of sRNA-target pairs identified pairs with an anticorrelated expression as well pairs showing other expressional relations pointing to a role of sRNAs in balancing transcriptional changes upon retrograde signals. Based on the comprehensive changes in sRNA expression we assume a considerable impact of sRNAs in retrograde-dependent transcriptional changes to adjust plastidic and nuclear gene expression. Significance statementPerturbations of plastid functions trigger retrograde signalling to adjust plastidic and nuclear gene expression, however, the role of small non-coding RNAs acting as regulators in these pathways is not well understood. We analysed small non-coding RNA expression in response to retrograde signals in A. thaliana wild type and two retrograde signalling mutants and identified members of all known small non-coding RNA classes pointing to a functional role of these RNA classes in retrograde pathways.

The production of reactive oxygen species (ROS) in response to cadmium (Cd) has been extensively studied, demonstrating that they play a key role in the plants response to this heavy metal. While the role of enzymes like RBOHs has been thoroughly studied, the function of other ROS-producing enzymes, such as peroxisomal glycolate oxidase (GOX), remains largely overlooked. Peroxisomal GOX is a core metabolic enzyme of the photorespiratory pathway occurring in chloroplasts, mitochondria and peroxisomes. Using Arabidopsis (Arabidopsis thaliana) mutants lacking the main peroxisomal GOX genes, GOX1 (gox1-1) and GOX2 (gox2-1) we explored their function in plant response to Cd. Although photosynthetic capacity appears to be affected to the same extent in both mutants under control and Cd stress conditions, GOX2 seems to play a greater role in ROS production in response to the metal. Transcriptomic analyses on WT and gox2-1 pointed to the mitochondrial electron transport chain (mETC) as a target of Cd stress. We further investigated the individual GOX1 and GOX2 functions in mETC regulation and redox state. Although oxidative ratio of mitochondria was higher in both mutants, it was more pronounced in the absence of GOX1. Furthermore, the mETC is affected in both mutants but the regulation of its components differs in each mutant. These results point out the different functions of the two photorespiratory GOX isoforms in Arabidopsis, leading to a better understanding of the photorespiratory pathway.

Tomato fruits normally accumulate large amounts of the red pigment lycopene in their chromoplasts. Some tomato cultivars (Solanum lycopersicum) show however distinct phenotypes, from a pure yellow hue to bicolor fruits with red and yellow sections. In this study, we show that alleles of the phytoene synthase 1 gene (PSY1), the first gene of carotenoid synthesis pathway, are responsible for the yellow, but also the bicolor phenotype. Introgression lines with the PSY1 allele from the green-fruited species S. habrochaites express less the enzyme, resulting in a bicolor phenotype. On the other hand, in tomato bicolor cultivars, the same coloration pattern is caused by a 3789 bp-deletion in the promoter region of PSY1. Since the deletion contains part of the 5UTR region of PSY1, translation efficiency is likely decreased resulting in a reduction of lycopene accumulation. Furthermore, we identified that the yellow ry phenotype is caused by a duplication and an inversion implicating PSY1 and the downstream neighbor gene. The genomic rearrangement change the end of PSY1 amino acid sequence. The fruits of yellow ry cultivars are still able in certain conditions to accumulate lycopene near the blossom-end of the fruit, though to a lesser extent than in bicolor cultivars. In contrast, fruits of the yellow r cultivars never present fleshy red sections. These cultivars have an insertion of a single long terminal repeat from the Rider transposon in the first exon of PSY1 resulting in a non-functional protein. These results demonstrate how multiple phenotypes can arise from structural variations in a key gene.

The detachment of organs is controlled by highly regulated molecular mechanisms. The position of the tomato abscission zone (AZ) is defined by the ratio of the proximal to distal part of the pedicel. In this study, the ratio was altered due to a shift in the position of the AZ which was attributed to shorter and longer pedicels of SlP4H3 RNAi and OEX lines due to changes on cell division and expansion in AZ and distal part. This might be associated with LM2- and JIM8-AGPs which increased in OEX and decreased in RNAi lines throughout the pedicel. The JIM13 AGPs were downregulated in the flower AZ of OEX lines, pointing to a role on abscission regulation. In addition, Co-IP in flower AZ with SlP4H3-GFP fusion proteins showed interaction with LM2-, JIM13- and JIM8-epitopes suggesting proline hydroxylation by SlP4H3. The lower content of methyl-esterified HGs and higher of demethyl-esterified HGs in the AZs of RNAi lines might be responsible for increased rigidity of the AZ cell walls, accounting for the higher force required for AZ tissue detachment to occur. Moreover, ethylene-induced flower abscission was accelerated in the RNAi lines and delayed in OEX lines, while exactly the opposite response was observed in the red ripe fruit AZs. This was partly attributed to alterations in the expression of cell wall hydrolases. Overall, these results indicate that P4Hs might regulate molecular and structural features of cell walls in the AZ as well as abscission progression by regulating the structure and function of AGPs. Sentence SummaryAlterations on the expression of tomato prolyl 4 hydroxylase 3 shifts the position of the pedicel abscission zone and alters ethylene induced abscission progression according to the developmental context of the pedicel.

As evidence mounts for ethylenes important role in sex determination, understanding ethylene signaling in Cannabis sativa L. (cannabis) has become increasingly vital. This study investigated the response of hemp-type and drug-type Cannabis sativa seedlings to ethylene, revealing a unique paired response phenotype under dark conditions and ethephon treatment, suggesting a more specialized variation of the triple response distinct from that observed in other species. Employing a novel ethephon-based assay, this research bypassed the complexities of using gaseous ethylene, providing a more accessible method for examining ethylene responses. The results showed C. sativa seedlings exhibit marked sensitivity to ethephon at concentrations (125 mg/L, 250 mg/L, and 500 mg/L) lower than those previously reported to influence mature plants, indicating a broad ethylene responsiveness across various genetic backgrounds. Furthermore, the reversal of ethylene-induced phenotypic changes by silver thiosulfate (STS) at all concentrations tested (1, 2, and 3 mM) suggests the conservation of ethylene signaling pathways in C. sativa. Importantly these phenotypic responses were observed in both drug and hemp type cannabis. However, the absence of an exaggerated apical hook in treated seedlings potentially points to a unique regulatory mechanism in response to ethylene in achene-bearing plants. These findings, highlighted by the successful induction of ethylene-sensitive phenotypes, underscore the conserved nature of ethylene signaling in C. sativa. The results highlight the need for further investigations into the regulatory mechanisms of ethylene in cannabis, especially concerning sexual development, opening new pathways for optimized breeding and cultivation practices aimed at enhancing plant growth and reproductive strategies.

Degradation of carotenoids in food crops during post-harvest storage results in major economic and nutritional losses. In this study, a pepper (Capsicum annuum) panel for post-harvest carotenoid retention was studied to elucidate underlying mechanisms associated with this commercial trait of interest. Quantitative determination of carotenoid pigments and concurrent cellular analysis indicated that those pepper fruit with thicker lipid exocarp layers and smooth surfaces, following post-harvest drying and storage, possessed increased carotenoid retention. Total cutin monomer content increased in high carotenoid retention fruits and sub-epidermal cutin deposits were responsible for the difference in exocarp thickness. Cutin biosynthesis and cuticle precursor transport genes were differentially expressed between high and low carotenoid retention genotypes, and this supports the finding that fruit cuticle biosynthesis is associated with carotenoid retention. Carotenoids were located within cells embedded within the sub-epidermal cutin layer, and these carotenoids were protected from degradation due to the lack of permeability of the fruit surface to reactive oxygen species, and their precursors. The identification of a novel role for the pepper fruit surface in protecting against carotenoid degradation serves as an important discovery for the function of the fruit cuticle and provides an exploitable resource to enhance fruit quality. Highlight statementCarotenoid pigments in Chilli pepper confer post-harvest colour and nutritional quality. Analysis of diverse commercial genotypes indicates the involvement of the fruit surface in carotenoid retention

Papaya (Carica papaya Linn.) is a tropical plant whose draft genome has been sequenced. Papaya produces large fruits rich in vitamins A and C and is an important cash crop in developing countries. Nonetheless, little is known about how the female gametophyte develops, how it is fertilized and how it develops into a mature seed containing an embryo and an endosperm. The Papaya female gametophyte displays a Polygonum-type architecture consisting of two synergid cells, an egg cell, a central cell, and three antipodal cells. Reports are available of the presumed existence of varieties in which cross fertilization is bypassed and autonomous development of embryos occurs (e.g., apomixis). In this study, we analyzed the development of female gametophytes in a commercial Hawaiian parental line and in the presumed apomictic Costa Rican line L1. Samples were collected before and after anthesis to compare the overall structure, size and transcriptional patterns of several genes that may be involved in egg and endosperm cell fate and proliferation. These genes were the putative papaya homologs of ARGONAUTE9 (AGO9), MEDEA (MEA), RETINOBLASTOMA RELATED-1 (RBR1), and SLOW WALKER-1 (SWA1). Our results suggest that its feasibly to identify structural features of Polygonum-type development, and that in bagged female flowers of line L1 we might have observed autonomous development of embryo-like structures. Possible downregulation of papaya homologs for AGO9, MEA, RBR1 and SWA1 was observed in embryo sacs from line L1 before and after anthesis, which may suggest a link between suspected apomixis and transcriptional downregulation of genes for RNA-directed DNA methylation, histone remodelers, and rRNA processing. Most notably, the large size of the papaya embryo sac suggests that it could be a cytological alternative to Arabidopsis thaliana for study. Significant variation in embryo sac size was observed between the varieties under study, suggesting wide differences in the genetic regulation of anatomical features.