High light can alleviate chilling stress in maize

Chilling stress has the potential to significantly decrease growth and yield of sensitive crop plants such as maize. Based on previous work, high light during chilling may exacerbate stress via enhanced photoinhibition but may also aid acclimation responses to chilling. To further understand molecular processes behind responses to chilling with and without high light, two maize accessions with contrasting tolerance (B73 and F7) were exposed to three treatments: chilling, chilling combined with high light and high light alone. Transcriptome data indicated that the chilling treatment resulted in the largest stress response. Addition of high light to chilling stress had a mitigating, rather than additive effect on stress, as evident from alleviated repression of photosynthesis-related genes and less induction of stress-related pathways such as abscisic acid signalling and senescence compared with the response to chilling alone. Five transcription factors belonging to well-known stress-related transcription factor families were identified as candidates for driving the transcriptional changes behind the high-light induced mitigation of chilling stress. Physiological measurements of non-photochemical quenching and the maximum quantum efficiency of photosystem II corroborated the transcriptome results, showing that the addition of high light alleviated photoinhibition and membrane damage caused by chilling. High light alone had little effect on the plant transcriptome or physiological response. Overall, this study overturns previous reports, offers a new outlook on the impact of high light during chilling stress and has the potential to provide clearer targets for crop engineering.