Arabidopsis LRR-MAL Receptor-like Kinases regulate intraspecific and interspecific pollen-stigma interactions

Flowering plants contain tightly controlled pollen-pistil interactions required for promoting intraspecies fertilization and preventing interspecies hybridizations. In Arabidopsis, several receptor kinases (RKs) are known to regulate the later stages of intraspecies pollen tube growth and ovular reception in the pistil, but less is known about RK regulation of the earlier stages. The Arabidopsis RKF1 cluster of Leucine-Rich Repeat Malectin (LRR-MAL) RKs was previously found to function in the stigma to promote intraspecies pollen hydration. Here, we tested additional combinations of up to seven Arabidopsis LRR-MAL RK knockout mutants for the RKF1 cluster, LIK1, RIR1 and NILR2. These LRR-MAL RKs were discovered to function in the female stigma to support intraspecies Arabidopsis pollen tube growth and to establish a pre-zygotic interspecies barrier against Capsella rubella pollen. Thus this study uncovered new biological functions for these poorly understood group of RKs in regulating the early stages of Arabidopsis sexual reproduction.