Study on the Relationship between High Temperature, Caryopsis Gene Expression, and Quality Formation in Rice (Oryza sativa L.)

• Main Authors: Shao-Kai Lin, 林韶凱
• Other Authors: Huu-Sheng Lur
• Format: Others
• Language: zh-TW
• Published: 2005
• Online Access: http://ndltd.ncl.edu.tw/handle/79832006608099601754

博士 === 國立臺灣大學 === 農藝學研究所 === 93 === Chapter 1 Proteins are essential to rice caryopsis development and quality formation. High temperature is an important environmental factor which may decrease grain quality. In the present study rice caryopsis proteins were profiled by two-dimensional polyacrylamide gel electrophoresis, and differentially expressed proteins were analyzed by liquid chromatography/tandem mass spectrometry (LC-MS/MS). Expressions of more than 400 polypeptide spots during caryopsis development, in response to temperature treatments or between varieties were monitored. Among them, more than 70 differentially expressed polypeptides were analyzed by LCMSMS and 54 proteins were identified with known functions. Of these, 21 were involved with carbohydrate metabolism, 14 with protein synthesis and sorting, and 9 with stress responses. Waxy (Wx) proteins and glutelins were the most prominous spots increased significantly during development. Allergen-like proteins, pyruvate orthophosphate dikinase and NADH-dependent sorbitol dehydrogenase, were also expressed during development, implying their physiological roles in caryopsis. Expression of large isoforms of Wx proteins was correlated with the amylose content of rice caryopsis. One protein with high GC content in its DNA sequence was correlated with the chalky trait of kernels. High temperature (35/30 ℃) decreased expression of Wx proteins, allergen-like proteins and elongation factor 1 β, but increased expression of small heat shock proteins (sHSP), glyceraldehyde-3-phosphate dehydrogenase and prolamin. The level of sHSP was positively correlated with the appearance of chalky kernels. During development, glutelins were phosphorylated and glycosylated, indicating these molecules were post-translationally modified. Possible functions of the expression of candidate proteins on grain quality are discussed. In addition, the expression of related genes at the RNA level were also monitored by RT-PCR. Chapter 2 Temperature is a major environmental factor on grains quality formation. High temperature may reduce rice grains quality. The components of starch and proteins are the other factors to influence the grain quality of rice. Under temperature influences, the final grain quality of caryopsis is determined by the physiological responses of biochemical processes and dry mass accumulation during caryopsis development. The present study focused on the relationship between the effects of high temperature on gene expression profilings and grain quality formation during developmental stages in rice caryopsis. The result of thermo-images analysis showed that rice panicles or grains dissipated heat slowly as compared to other organs, implying that rice panicles may be more sensitive and vulnerable to high-temperature environment. High temperature leads to decrease in panicle weight, filled spikelets rate, thousand spikelets weight and grains yield; produced sever chalky appearance kernels on panicles. High temperature influenced endosperm cell differentiation and reduced DNA endoreduplication. In japonica type rice, high temperature also resulted in lower amylose and protein contents. In grain physical chemical properties, high temperature decreased viscosity but increased pasting temperature and gel consistency of brown rice flour. At molecular basis, high temperature reduced the expression of GBSS in Japonica rice varieties; as TNG67, however, high temperature enhanced starch synthase II gene expression in Indica rice varieties, as TN1. Either the decrease of GBSS or increase of starch synthase II would lead to a lower amylase ratio in rice grains. Prolamins contents declined in mature rice grains of all three cultivars grown at high temperature. However, the effects of high temperature on storage proteins were different with varieties. The changing in amylose and protein contents may cause the observed negative effect of physical chemical characteristics of the rice flour. In addition, high temperature could enhance the proteins expression of 16.9c HSP, 17.9 HSP, 18 HSP, glyceraldehyde-3- phosphate dehydrogenase and elongation factor 1 beta, while reduced the expression of nucleotide diphosphate kinase and allergen-like proteins. Based on the present results, high temperature caused a complex physiological and metabolic responses related to starch and protein accumulation and packing in rice grains. Thus resulted in defective quality of rice grain. A schematic model has been proposed to depict the influence of high temperature on grain quality formation in rice.