Abstract
Our previous study has shown that nitrogen plays an important role in dealing with significantly increased chalkiness caused by elevated temperature. However, the role of nitrogen metabolites has not been given sufficient attention, and its regulatory mechanism is not clear. This study investigated the effects of high temperature and nitrogen fertilizer on the synthesis of grain storage protein and further explored the quality mechanism under the actual scenario of field warming. Results showed that increased temperature and nitrogen fertilizer could affect the activities of nitrogen metabolism enzymes, namely, glutamate synthetase, glutamine synthetase, glutamic pyruvic transaminase, and glutamic oxaloacetic transaminase, and the expressions of storage protein synthesis factor genes, namely, GluA and GluB, and subfamily genes, namely, pro14, BiP1, and PDIL1, which co-induced the changes of storage protein synthesis in rice grains. Furthermore, the increased temperature changed the balance of grain storage substances which may lead to the significantly increased chalky rate (197.67%) and chalkiness (532.92%). Moreover, there was a significant negative correlation between prolamin content and chalkiness, indicating that nitrogen fertilizer might regulate the formation of chalkiness by affecting the synthesis of prolamin. Results suggested that nitrogen application could regulate the related core factors involved in nitrogen metabolism pathways, which, in turn, affects the changes in the storage protein components in the grain and further affects quality. Therefore, as a conventional cultivation measure, nitrogen application would have a certain value in future rice production in response to climate warming.
Highlights
With the improvement of living standards of people, the demand for high-quality rice is increasing
In this study, the most prominent results of the effect of increasing temperature on the rice quality were the significantly increased chalky rice rate (197.67%), chalky area (104.62%), and chalkiness (532.92%)
Endosperm Development The effects of elevated temperature and nitrogen on the development of grain endosperm were investigated, and the results showed that there was no amyloplast found in CK and CKN treatments, while a small amount of amyloplasts and protein bodies (PBs) I and PB II were observed in ETN at 6 days after anthesis (DAA)
Summary
With the improvement of living standards of people, the demand for high-quality rice is increasing. With the intensification of global warming, the increase of chalkiness in rice quality traits has become a key issue that needs to be focused on. Studies conducted by artificial climate room (Xu et al, 2020) and actual field warming experiments (Rehmani et al, 2014) illustrated that high temperature was Nitrogen Fertilizer Reduced Chalkiness conducive to the occurrence of chalkiness (Mitsui et al, 2013). Nitrogen application is a simple agronomic measure, which has been proved that it can alleviate high-temperature damage through decelerating the early grain-filling rate of rice and could further reduce the occurrence of chalkiness (Dou et al, 2017; Tang et al, 2019). The regulatory effect of nitrogen on the physicochemical properties of rice starch had been preliminarily clarified in our previous study, the characteristics of its effects on grain nitrogen metabolism have not yet been investigated
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