Kromdijk, J. — Page 2 | bioRxiv Science

bioRxiv2023

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.

plant biology↗

bioRxiv2020

The rice bundle sheath produces reactive oxygen species during high light stress via NADPH oxidase

When exposed to high light plants produce reactive oxygen species (ROS). In Arabidopsis thaliana local accumulation of ROS preferentially takes place in bundle sheath strands, but little is known about how this response takes place. Using rice and the ROS probes diaminobenzidine and 2,7-dichlorodihydrofluorescein diacetate, we found that after exposure to high light, ROS were produced more rapidly in bundle sheath strands than mesophyll cells. This response was not affected either by CO2 supply or photorespiration. Consistent with these findings, deep sequencing of mRNA isolated from mesophyll or bundle sheath strands indicated balanced accumulation of transcripts encoding all major components of the photosynthetic apparatus. However, transcripts encoding several isoforms of the superoxide/H2O2-producing enzyme NADPH oxidase were more abundant in bundle sheath strands than mesophyll cells. ROS production in bundle sheath strands was reduced by blocking NADPH oxidase activity pharmacologically, but increased when the bundle sheath preferential RBOHA isoform of NADPH oxidase was over-expressed. NADPH oxidase mediated accumulation of ROS in the rice bundle sheath was detected in etiolated leaves lacking chlorophyll indicating that high light and NADPH oxidase-dependent ROS production is not dependent on photosynthesis.

plant biology↗