Physiological, biochemical and electron microscopy analyses were used to investigate the photosynthetic performance of flag leaves in rice white stripe mutant 6001 during the senescence process. Results showed that the chlorophyll content at the heading and milk-ripe stages in rice mutant 6001 were about 34.78% and 3.00% less than those in wild type 6028, respectively. However, the chlorophyll content at the fully-ripe stage in rice mutant 6001 was higher than that in wild type 6028. At the heading stage, the net photosynthetic rate(Pn) in rice mutant 6001 was lower than that in wild type 6028. Rice mutant 6001 also exhibited a significantly slower decrease rate of Pn than wild type 6028 during the senescence progress, especially at the later stage. Furthermore, Ca2+-ATPase, Mg2+-ATPase and photophosphorylation activities exhibited the similar trends as the Pn. During the senescence process, the 68 k Da polypeptide concentrations in the thylakoid membrane proteins exhibited a significant change, which was one of the critical factors that contributed to the observed change in photosynthesis. We also observed that the chloroplasts of rice mutant 6001 exhibited higher integrity than those of wild type 6028, and the chloroplast membrane of rice mutant 6001 disintegrated more slow during the senescence process. In general, rice mutant 6001 had a relatively slower senescence rate than wild type 6028, and exhibited anti-senescence properties.
Translational control of gene expression,including recruitment of ribosomes to messenger RNA(mRNA),is particularly important during the response to stress.Purification of ribosomeassociated mRNAs using translating ribosome affinity purification(TRAP)followed by RNAsequencing facilitates the study of mRNAs undergoing active transcription and better proxies the translatome,or protein response,to stimuli.To identify plant responses to Magnesium(Mg)deficiency at the translational level,we combined transcriptome and translatome analyses.Excitingly,we found 26 previously unreported Mg-responsive genes that were only regulated at the translational level and not the transcriptional level,during the early response to Mg deficiency.In addition,mutants of the transcription factor ELONGATED HYPOCOTYL 5(HY5),the H^(+)/CATION EXCHANGER 1 and 3(CAX1 and CAX3),and UBIQUITIN 11(UBQ11)exhibited early chlorosis phenotype under Mg deficiency,supporting their functional involvement in ion homeostasis.Overall,our study strongly supports that TRAP-seq combined with RNA-seq followed by phenotype screening could facilitate the identification of novel players during stress responses.
