Overexpression mutants reveal a role for a chloroplast MPD protein in regulation of reactive oxygen species during chilling in Arabidopsis

Reactive oxygen species (ROS) contribute to cellular damage in several different contexts, but their role during chilling damage is poorly defined. Chilling sensitivity both limits the distribution of plant species and causes devastating crop losses worldwide. Our screen of chilling-tolerant Arabidopsis (Arabidopsis thaliana) for mutants that suffer chilling damage identified a gene (At4g03410) encoding a chloroplast Mpv17_PMP22 protein, MPD1, with no previous connection to chilling. The chilling-sensitive mpd1-1 mutant is an overexpression allele that we successfully phenocopied by creating transgenic lines with a similar level of MPD1 overexpression. In mammals and yeast, MPD1 homologs are associated with ROS management. In chilling conditions, Arabidopsis overexpressing MPD1 accumulated H2O2 to higher levels than wild-type controls and exhibited stronger induction of ROS response genes. Paraquat application exacerbated chilling damage, confirming that the phenotype occurs due to ROS dysregulation. We conclude that at low temperature increased MPD1 expression results in increased ROS production, causing chilling damage. Our discovery of the effect of MPD1 overexpression on ROS production under chilling stress implies that investigation of the nine other members of the Mpv17_PMP22 family in Arabidopsis may lead to new discoveries regarding ROS signaling and management in plants.

[Chilling damage comprehensive assessment methods for rice.]

Based on the grey correlation analysis method, the chilling damage inducing factors and yield structure traits of rice in different growth stages, and the yield structure traits and final yield of rice were regarded as two grey systems. By seeking the grey relations of the grey systems and using the multi level grey correlation analysis method, the comprehensive assessment model of rice chil-ling damage was constructed, and the comprehensive assessment indices of chilling damages in sepa rate stages were established. The rice chilling damages at 27 stations in Northeast China from 1961 to 2015 were assessed separately. The results showed that there was a good corresponding relationship between the chilling damage and the rice yield. The low temperature during the vegetative growth stage, the vegetative growth and reproductive stage, the pollination stage or the grain filling stage significantly decreased the panicle number per plant, the average panicle grain number or the thousand kernel mass, and increased the empty grain rate. A good correspondence existed between temperature and rice yield in the typical chilling damage years.