Abstract: 【Objective】The objective of this study is to identify the differentially expressed proteins and their biological functions involving in rice grain responding to high temperature stress at the early milky stage.【Method】The heat-tolerant rice line XN0437T and the heat-sensitive rice line XN0437S were used as plant materials. The tub-planting method and conventional cultivation way were used to culture the rice. To ensure that only uniformly developed samples were used for analysis, rice ears were labeled on the same heading date and the panicles on the labeled ears were further labeled on the same flowering date. On the 10th day after heading, plants with the same label were transferred to chambers and maintained at a temperature of 38.0/25.0 ± 0.5℃ (treatment / control) for 1 day, 3days and 5days. After the initiation of high temperature stress at the early milky stage of rice, rice grains from the same region (middle to bottom part) of labeled ears were harvested at three different time points. The total proteins from harvested sample were extracted by the trichloroacetate (TCA) - acetone precipitation method and the protein profiles of rice grain were set up by two-dimensional electrophoresis (2-DE). The proteins in rice responding to high temperature stress (PRHT) were firstly identified by comparing the 2-DE protein profiles between treatment and its parallel control for heat-tolerant and -sensitive lines, respectively. The differentially expressed proteins were then confirmed by comparing the volume of PRHT from heat-tolerant and -sensitive lines. The functions of these differentially expressed proteins were identified by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight mass spectrometry (MALDI-TOF/TOF MS) analysis and protein database searching. 【Result】Twenty-seven differentially expressed protein spots were found and showed more than 2-folds difference in PRHT volume between the heat-tolerant and -sensitive lines, and 25 proteins were identified by MS and database searching. The 25 identified proteins were involved in biological synthesis (10 proteins), energy metabolism (4 proteins), oxidation (7 proteins), emergency response (3 proteins) and transcriptional regulation (1 protein). 【Conclusion】The expression patterns of the rice grain proteins, which are involved in biological synthesis, energy metabolism, oxidation, emergency response and transcriptional regulation, were influnced by high temperature stress at early milky stage of rice grain. The expression patterns of these proteins were showed variable according to the difference in rice genetype (heat-tolerant and -sensitive lines) and extent (days) of high temperature treatment.

Key words: rice , early milky stage , rice grain , high temperature stress , proteomics