Multiple regulators were involved in glutelin synthesis and subunit accumulation in response to temperature and nitrogen during rice grain-filling stage

Rice glutelin is sensitive to temperature and nitrogen, however, the regulatory mechanism of glutelin response to temperature and nitrogen is unclear. In this study, we conducted the open field warming experiment by the Freeair temperature enhancement facility and application of nitrogen during grain filling. In three-year field warming experiments, glutelin relative content was significantly increased under elevated temperature and application of nitrogen. Temperature and nitrogen and their interaction increased the glutelin accumulation rate in the early and middle grain filling stages (10-25d after fiowering), but decreased the glutelin accumulation rate in the middle and late grain filling stages (25-45d after fiowering). Elevated temperature promoted pro-glutelin levels whereas application of nitrogen under warming increased the amount of & alpha;-glutelin. At the transcriptional level, the expression levels of the glutelin-encoding genes and protein disulphide isomerase-like enzyme (PDIL1-1), glutelin precursor accumulation 4 (GPA4), glutelin precursor mutant 6 (GPA2), glutelin precursor accumulation 3 (GPA3) and vacuolar processing enzyme (OsVPE1) of glutelin folding, transport and accumulation-related genes were upregulated by nitrogen under natural temperature as early as 5d after fiowering. However, elevated temperature up-regulated glutelin-encoding genes before 20d after fiowering, and the expression of endoplasmic reticulum chaperone (OsBip1), OsPDIL1-1, small GTPase gene (GPA1), GPA2-GPA4 and OsVPE1 were significantly increased post 20d after fiowering under warming. In addition, the increase in glutelin content worsened grain quality, particularly chalkiness and eating quality. Overall, the results were helpful to understand glutelin accumulation and provide a theoretical basis for further study the relationship between rice quality and glutelin under global warming.

Automated summary

This study found that rice glutelin is sensitive to temperature and nitrogen, and their interactions can affect glutelin accumulation during grain filling. Elevated temperature promotes the levels of pro-glutelin and application of nitrogen under warming increases the amount of α-glutelin. However, the increase in glutelin content worsens grain quality, particularly chalkiness and eating quality.