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Cotton is an important cash crop, and its cultivation area, wide distribution, strong adaptability. China's cotton acreage currently stabilized at 8000 mu, total output reached 7,000,000 tons, the main byproduct of cotton production reached 13 million tons of cottonseed. Cottonseed kernels are rich in oil, content of 30% -45%, and is an important fuel source. But so far, the formation of domestic and foreign oil related genes on cotton are few reports on the study. In this study, 7124 developing island cotton seed material, the use by CLONTECH Creator TM SMARTM PCR cDNA Library Construction Kit to build a sea-island cotton seed oil formation stage cDNA library. The constructed library storage capacity of primary 5 × 10 6 , library titer of 1.5 × 10 8 cfu · mL -1 . In the library of 180 randomly picked clones were PCR analysis showed that the length of the inserted fragment between mainly concentrated in the 1.0-2.0 kb. 2170 randomly picked clones for the 3 'end unidirectional sequencing were obtained valid serial 1831, the average length of the sequence 423bp, which contains Unigenes1459 amended. The obtained all the NCBI EST sequence database BLAST nt and nr compared with 67.51% of the EST sequences shows the nucleic acid sequence has a high degree of homology; with 75.12% of the EST sequences compared with existing protein high homology; Total 38 EST sequence shows the formation of lipid associated with, accounting for 2.60 percent of all Unigenes. Phosphoenolpyruvate carboxylase (PEPC) is a CO 2 immobilized enzyme, which catalyzes from phosphoenolpyruvate (PEP) oxaloacetate (OAA) reaction in energy and biosynthetic metabolism play multiple roles. In this study, according to a published EST sequences pepc gene and chromosome walking by RACE (GenomeWalking) technology from Sea Island cotton in 7124 pepc cloned a new gene named Gb.pepc3. The sequence length of 3259bp, contains a 2910 bp open reading frame encoding 969 amino acids, suggesting a molecular weight of 110.7 Kd, isoelectric point of 6.08 I. On Gb.pepc3 protein homology alignment and phylogenetic analysis showed Gb.pepc3 and other plants have been reported C3-pepc similarity is very high, above 75%. Quantitative PCR showed Gb.pepc3 organizations in the cotton is widespread among the highest expression in the embryo, in the fiber expression is lower. In various stages of seed development Gb.pepc3 expression varies: Sea Island cotton 15 days after flowering Gb.pepc3 expression peaked, and upland cotton flowering 20 days Gb.pepc3 expression reached its peak. And inter-island cotton and upland cotton significantly different expression. Cotton pepc pepc genes for gene cloning research and application is important, help to understand the mechanism of photosynthesis of cotton, cotton seed oil points to improve the content to provide theoretical and technical support.
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