Study On The Physiological Basis Of Temperature Stability Of Rice Fertility And Photosynthesis

Temperature is one of the main ecological factors that effect plant growth and development, the change of which will arose the plant complicated physiological responses. At present, discussion on rice genetic and physiological basis in high temperature adaptation and the countermeasures of the global temperature rising is one of the important hotspots that research rice. Moreover, fertility of photo-thermo-sensitive genic male sterile (PTGMS) rice is accurately regulated by temperature changes. So, research on the gene expression that regulates fertility by temperature has an important meaning to illustrate the basis in fertility stability of PTGMS rice and enrich the theoretical foundation of two line hybrid rice in China. Two aspects mentioned above were discussed in this paper.1. Study on the physiological basis of high temperature stability of photosynthesis (HTSP)The leaves are the major organ that accepts temperature changes, the basic function of which is photosynthesis. And HTSP of leaves is the important index that evaluates high temperature stability. In this study, Shuhui527-high temperature tolerant representative and Texianzhan-high temperature susceptible representative were screened on the basis of identification of HTSP in tens of different rice varieties, were used, and a series of physiological differences under high temperature were analyzed. The vascular bundle's microstructure and stomata characteristics investigated, temperature response of differential proteins expression, stability of synthetic contents of protein in enzyme-extracting solution and large and small subunit of Rubisco, physiological indexes determinated were analyzed by comparative physiological methods, and some primary results were obtained. These could accumulate foundation for physiological and differently expressed characteristics under high temperature stress and further study on the resistant/tolerant mechanism to high temperature. The results were as follows:(1) High temperature tolerant cultivar of photosynthesis-Shuhui527 (T- Shuhui527) has the stable physiological characteristics. Because it could maintain the more stable cell membrane structure and higher proline level, resulting in photosynthetic organs' better suitable ability of high temperature stress, as a result, T-Shuhui527 could keep more stable photosynthesis.(2) T-Shuhui527 and high temperature susceptible cultivar of photosynthesis-Texianzhan (S-Texianzhan) expressed the different kinds of heat shock proteins (HSP) under high temperature stress by two-dimensional gel electrophoresis method. S-Texianzhan expressed four kins of HSP, all classified to large HSP (laHSP), with molecular weights (MW) ranging from 63.5 kD to 76.8 kD and isoelectric points (pI) from 4.74 to 5.31. And T-Shuhui527 also expressed four kins of HSP, but all classified to small HSP (smHSP), with molecular weights (MW) ranging from 16.3 kD to 23.3 kD and isoelectric points (pI) from 4.80 to 5.91. It is remarkable that only one kind of HSP was induced completely in T-Shuhui527, others were the heat shock cognate proteins (HSC) with the differentially expressed levels.(3) The contents of protein in enzyme-extracting solution and large and small subunit of Rubisco in flag leaves of T-Shuhui527 indicated much higher thermal stability when compared to S-Texianzhan.(4) Compared to S-Texianzhan, more developed vascular bundles of main vein of flag leaf and the second internode, and higher stomatal density on epidermis and particular stomatal character of flag leaf were observed in T-Shuhui527.2. Research on molecular mechanism of different temperature sensitivity of male fertility of PTGMS riceThe natural illumination and temperature are two important factors that influced the male fertility of PTGMS rice. The former variation is well-regulated, but the latter is untraceable. The critical sterility temperature point (CSTP) of PTGMS lines is the crucial index that evaluates the stability of male sterility. Badly, CSTP of almost all PTGMS lines identified presents unstability, which seem to have the tendency to gradually increase their CSTP and thus producing fertile pollens under the previous sterile conditions. Some originally qualified PTGMS lines therefore have gradually become ineligible after several generations of propagation. This is the key technical obstacle present in two- line hybrid rice development.In this study, P2364S and P2864S with CSTP of 23℃and 28℃respectively, near isogenic lines of PTGMS rice Peiai 64S were used. The gene expression of spikelet during thermo-sensitive period of fertility transition was analyzed using expression profile genechip technology. The physiology and differential genetic expression at transcriptional level were compared between P2364S and P2864S, and, molecular mechanism of temperature sensitivity of male fertility of PTGMS rice was discussed. GeneChip Rice Genome Array was used, which contained 57381 probe sets representing the expressed sequences of rice japonica and indica cultivars. The results showed that: 1334 probe sets were up- or down-regulated at least 2 fold, accounted for 2.32% of overall probe sets numbers. 73 probe sets up- or down-regulated at least 16 fold expressed differentially were analyzed using bioinformatic methods through the public databases. Among these, there were 55 probe sets having putative functions, which related to electron and proton transport, translation, cell growth and development, resistance, signal transduction, material metabolism, transposon and transcription. After analyzed, the genes related to resistance, signal transduction and transposon may have the relationship with temperature sensitivity of male fertility of PTGMS rice. The analysis and validation of major functional genes need further study.