| Leymus chinensis (Trin.) Tzvel., a member of Poaceae, is a dominating grass species distributed in eastern grasslands in Eurasia. As the king of forage, it is a strategic biologieal resource with technological advantage in our country and has an important role in stock raising and environmental protection in Northern China.The low sexual reproduction restricted its application and from the point of experimental biology, initial researches have been done to study its characterizations of sexual reproduction and to explore its mechanism by cellular and modern molecular technology. The main results in this paper are listed as below:1. Self-incompatibility (SI) is discovered in L. chinensis on our experiments. In 6 populations, seed set was between 6.5% - 56.7% under natural environments, and between 0.6% - 4.3% when selfing. They were significant different. More than 92.2% pollens were detected viable in mature anthers by FDA florenscens staining. The developmental characters of pistals and stamina at time and space were observed and they were suitable for both selfing and outcrossing. The pollen-stigma compatibility tests showed that 5.5%-11.7% of selfing pollens were compatible and 60.0%-84.8% of outcrossing pollens were compatible. This indicated that the germination of selfing pollen tubes was restrained on stigmas. Secondly, incompatible pollen tubes grew slowly or stopped when they just entered into the stigma under fluorescence microscope.2. The SI mechanism in L. chinensis was initially determined as Gametophytic. The experiment was conducted with a sister family. The scope of pollen-stigma compatible rates in selfing combination was observed between 0 % - 6.9 % and that in outcrossing combination was larger (47.5 -96.0 %) and distributed continuously. And the results between reciprocal cross (88.2%) were consistent.3. Some variance extents of seed set existed in a population. Experimental with several plants showed mean seed set under selfing, reciprocal cross and open pollination were 4.59%, 18.1% and 35.7%, respectively, and the variance coefficient among plants were 33.4%, 21.2% and 17.1%, respectively. The differences among plants reached the significant level. Some correlation between selfing, outcrossing or open pollination existed and this showed that the seed set differences among plants were related to their physiology of themselves.4. Thioredoxin h gene in L. chinensis (ThiohLc) was isolated and it was analyzed. The full length and cDNA sequences were cloned. DNA sequence had 3 introns and 4 exon with 2257 bp. Compared with Thio h cDNA from 0. sativa, they had identity with 32.0%. Using Southern blotting, gene ThioLc was estimated to be one copy in L. chinensis genome. Northern blotting indicated that ThioLc did not express in leaves, roots, stems, and young pistils, but expressed in young pollens and mature pistils. The highest expression level of ThioLc was detected in mature pollens. These results showed that ThiohLc is pollen-specified.5. ThiohLc protein that expressed in Escherichia coli displayed highly typicalthioredoxin activity. After ThiohLc expression vector was constructed, ThioLc was expressed as recombinant protein in E. coli and purified by the high affinity for Ni-NTA resin. In the nonspecific insulin reduction assay, the protein displayed typical thioredoxin activity in vitro. Its Vmax and Km could be calculated and the protein could be used to look for its target protein in vivo.
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