Quality protein maize (QPM) (Zea mays L.) varieties contain enhanced levels of tryptophan and lysine, exhibiting improved nutritive value for humans and livestock.  However, breeding QPM varieties remains challenging due to the complex process of rebalancing storage protein.  This study conducted transcriptome and proteome analyses to investigate the process of storage proteins rebalancing in opaque2 (o2) and QPM.  We found a weak correlation between the transcriptome and proteome, suggesting a significant modulating effect of post-transcriptional events on non-zein protein abundances in Mo17o2 and QPM.  These results highlight the advantages of proteomics.  Compared with Mo17, 672 differentially expressed proteins (DEPs) were identified both in Mo17o2 and QPM, and several of them were associated with storage protein, starch, and amino acid synthesis.  We identified 178 non-zeins as DEPs in Mo17o2 and QPM kernels.  The up-regulated non-zein DEPs were enriched in lysine, tryptophan, and methionine, which affected the protein quality.  Co-expression network analysis identified regulators of storage protein synthesis in QPM, including O2, PBF1, and several transcription factors.  Our results revealed how storage protein rebalancing occurs and identified non-zein DEPs that may facilitate superior-quality QPM breeding. 

Silicon can improve drought tolerance of plants, but the mechanism still remains unclear.  Previous studies have mainly concentrated on silicon-accumulating plants, whereas less work has been conducted in silicon-excluding plants, such as tomato (Solanum lycopersicum L.).  In this study, we investigated the effects of exogenous silicon (2.5 mmol L^–1) on the chlorophyll fluorescence and expression of photosynthesis-related genes in tomato seedlings (Zhongza 9) under water stress induced by 10% (w/v) polyethylene glycol (PEG-6000).  The results showed that under water stress, the growth of shoot and root was inhibited, and the chlorophyll and carotenoid concentrations were decreased, while silicon addition improved the plant growth and increased the concentrations of chlorophyll and carotenoid.  Under water sterss, chlorophyll fluorescence parameters such as PSII maximum photochemical efficiency (F_v/F_m), effective quantum efficiency, actual photochemical quantum efficiency (Ф_PSII), photosynthetic electron transport rate (ETR), and photochemical quenching coefficient (q_P) were decreased; while these changes were reversed in the presence of added silicon.  The expressions of some photosynthesis-related genes including PetE, PetF, PsbP, PsbQ, PsbW, and Psb28 were down-regulated under water stress, and exogenous Si could partially up-regulate their expressions.  These results suggest that silicon plays a role in the alleviation of water stress by modulating some photosynthesis-related genes and regulating the photochemical process, and thus promoting photosynthesis.