Knockdown of GDCH gene reveals reactive oxygen species‐induced leaf senescence in rice

Glycine decarboxylase complex ( GDC ) is a multi‐protein complex, comprising P ‐, H ‐, T ‐ and L ‐protein subunits, which plays a major role in photorespiration in plants. While structural analysis has demonstrated that the H subunit of GDC ( GDCH ) plays a pivotal role in GDC , research on the role of GDCH in biological processes in plants is seldom reported. Here, the function of GDCH , stresses resulting from GDCH ‐ knockdown and the interactions of these stresses with other cellular processes were studied in rice plants. Under high CO 2 , the OsGDCH RNA interference ( OsGDCH ‐ RNAi ) plants grew normally, but under ambient CO 2 , severely suppressed OsGDCH ‐ RNAi plants ( SSPs ) were non‐viable, which displayed a photorespiration‐deficient phenotype. Under ambient CO 2 , chlorophyll loss, protein degradation, lipid peroxidation and photosynthesis decline occurred in SSPs . Electron microscopy studies showed that chloroplast breakdown and autophagy took place in these plants. Reactive oxygen species ( ROS ), including O 2 − and H 2 O 2 , accumulated and the antioxidant enzyme activities decreased in the leaves of SSPs under ambient CO 2 . The expression of transcription factors and senescence‐associated genes ( SAG s), which was up‐regulated in SSPs after transfer to ambient CO 2 , was enhanced in wild‐type plants treated with H 2 O 2 . Evidences demonstrate ROS induce senescence in SSPs , and transcription factors OsWRKY72 may mediate the ROS ‐induced senescence.