Relationship between polyamines and the formation of grain quality during grain-filling stage under high temperature
Date Issued
2012
Date
2012
Author(s)
Hsu, Shu-Hwa
Abstract
High temperature during the gain-filling stage can increase chalky appear-ance and reduce weight of rice grains. Our previous studies showed that high temperature can reduce polyamine level of rice grains, and application of nitrogen fertilizer can reduce the chalkiness of rice grains. However, the relationship between polyamines level and nitrogen fertilizer during rice grain filling stage at high temperature is still unclear. In order to understand the role of polyamine and its relationship with nitrogen in developing rice grains under high temperature, rice cultivar TK 9 was used as material in this experiment. After flowering, TK 9 was exposed to high temperature for 15 days with or without nitrogen addition during grain filling stage. Grain quality, major storage protein and physiolocal responses were determined after harvest. Polyamine levels of developing rice caryopsis were analyzed by HPLC. Real-time quantitative PCR was further utilized to determine the gene expression of key genes in response to high temperature and nitrogen application.
The results showed that high temperature caused deleterious effects on the yield and quality of rice grains. Applying nitrogen increased dry matter and major storage proteins content, while reduced chalkiness grain ratio. Physiological analysis showed that nitrogen moderated the deleterious ef-fects of high temperature by delaying chlorophyll degradation of pericarp and reducing Malondialdehyde (MDA) concentration. In developing caryopsis, the major polyamine was spermidine (Spd), followed by putrescine (Put) and Spermine (Spm), regardless of temperature treatments. Nitrogen application recovered the decreased level of polyamine under high temperature. In further gene expression analysis, high temperature repressed genes expression related to biosynthesis of starch and protein, such as GBSS, Pro7 and Glu, whereas elevated the expression of hypoxia fermentation-related genes, such as pyruvate decar-boxylase (PDC) and alchol dehydrogenase (ADH). In addition, high temperature enhanced expression of PAO gene, which led to reduction of Spd level and release of hydrogen peroxide (H2O2). High temperature also enhanced expression of the cell death related gene PBZ. On the other hand, nitrogen application repressed expression of PAO gene under high temperature, suggesting that nitrogen prevented degradation of spd and alleviated oxidative stress. Under high temperature, external applycation of spd or 1, 8-diaminooctane (1, 8-DO, PAO inhibitor) sustained caryopsis chlorophyll content and grain weight, but reduced accumulation of H2O2 and MDA. The present findings suggest that the decreased level of polyamines may be involved in high temperature induced defective caryopsis traits, and the nitrogen application can ameliorate the deleterious effects of high temperature by inhibiting the expression of PAO gene.
Subjects
high temperature
polyamine
rice
SDGs
Type
thesis
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