Influences of Temperature on the Expression of Grain Proteins during Filling Stage in Rice (Oryza sativa L.)

• Main Authors: Shao-Kai Lin, 林韶凱
• Other Authors: Huu-Sheng Lur
• Format: Others
• Language: zh-TW
• Published: 2000
• Online Access: http://ndltd.ncl.edu.tw/handle/66749817605091788370

碩士 === 國立臺灣大學 === 農藝學研究所 === 88 === Temperature and light are two major factors that influence rice cultivation in Taiwan. Changes in temperature are significant between the cultivated environments of the first and second crops, and are generally being taken as one of major reasons affecting grain quality of cropping season. Among chemical constituent of rice grains, proteins have a decisive influence in the chemical and physical properties, nutritive value, and appearance of rice grains. Accumulation of rice proteins is affected directly by temperature. Therefore, study of the biosynthetic process of rice proteins and their responses to environment would benefit the knowledge for improving the quality of rice. Although molecular mechanisms of the biosynthesis for storage proteins have been studied to a certain extent in rice, how the environment affects on endosperm proteins are still unclear. The main objectives of this study were to study the temperature effects on the expressions of rice grain proteins using a concept of “proteomics”. A japonica cultivar (Tainung 67, TNG67) and a indica cultivar (Taichung Native 1, TC(N)1) were grown in pots at a phytotron under 30/25 ºC (day/night). At flowering the plants were moved to 35/30ºC, 30/25ºC, and 20/15 ºC for temperature treatments. Grains were sampled at 6, 9, 12, and 15 days after flowering, and endosperm were dissected for analysis. Fresh weight, levels of dry weight, water content, nuclei number, soluble protein, prolamins, and glutelins were measured. To determine the expression pattern of endosperm proteins, a high resolution two-dimensional gel electrophoresis system (2-DE) was used, with iso-electric focusing (IPG) in the first dimention and sodium dodecyl sulfate- polyacrylamide gel electrophoresis in the second dimention. The results showed that, in general, plant growth and all physiological processes were slowed down under low temperature. Cultivar TC(N)1 (indica type) was more sensitive to low temperature than TNG67. Under high temperature, however, TC(N)1 had higher rate in the increase of fresh weight and endosperm cell number and soluble proteins than did the TNG67. Glutelins level was significantly higher than prolamins for both cultivars. And the accumulation/expression of glutelins was also earlier than that of prolamins. A total of 300 to 400 protein polypeptides could be resolved by 2-DE electrophoresis. The expressions of polypeptides were further quantified and characterized by their coordinate molecular masses, pI, and expression time course. The expression patterns of protein polypeptides in TNG67 were significantly affected by high temperature. But in TC(N)1 the expression patterns were sensitive to low temperature. Expression of near 33 polypeptides in TNG67 and near 32 polypeptides in TC(N)1 could be regulated by temperature. During endosperm development the amounts of 16 polypeptides in TNG67 and 14 polypeptides in TC(N)1 were increased. And the levels of 7 polypeptides in TNG67 and 6 polypeptides in TC(N)1 were decreased during endosperm development. The sequencing analysis based on Edman degradation theory has not been successful for most of the polypeptides. That may be attributed to a general high glycosilation character occurring at the N-terminal of seed proteins. A more advanced technique for polypeptide sequencing, called “in-gel digestion”, is expected to be conducted. The sequences and functions of these endosperm protein, thus, can be unveiled.