The plant mitochondrial genome displays complex features, particularly in terms of cytoplasmic male sterility(CMS). Therefore, research on the cotton mitochondrial genome may provide important information for analyzing genome evolution and exploring the molecular mechanism of CMS. In this paper, we present a preliminary study on the mitochondrial genome of sea island cotton(Gossypium barbadense) based on positive clones from the bacterial artifi cial chromosome(BAC) library. Thirty-fi ve primers designed with the conserved sequences of functional genes and exons of mitochondria were used to screen positive clones in the genome library of the sea island cotton variety called Pima 90-53. Ten BAC clones were obtained and verifi ed for further study. A contig was obtained based on six overlapping clones and subsequently laid out primarily on the mitochondrial genome. One BAC clone, clone 6 harbored with the inserter of approximate 115 kb mtDNA sequence, in which more than 10 primers fragments could be amplifi ed, was sequenced and assembled using the Solexa strategy. Fifteen mitochondrial functional genes were revealed in clone 6 by gene annotation. The characteristics of the syntenic gene/exon of the sequences and RNA editing were preliminarily predicted.
SU Ai-guoLI Shuang-shuangLIU Guo-zhengLEI Bin-binKANG Ding-mingLI Zhao-huMA Zhi-yingHUA Jin-ping
Cotton(Gossypium)is an important crop providing textile fiber and edible oil.To gain the insights into mechanism of the cytoplasmic male sterility(CMS)inheritance,we constructed five fosmid libraries of mitochondrial genomes from mitotype of G.harknessii Brandegee.(one CMS line and its restorer),mitotype of G.hirsutum L.(one CMS line and its maintainer),and G.barbadense L.The numbers of the clones in these libraries ranged from 1152 to 2016 with an average insert size of 36.2 to 38.4 kb,equivalent to 70–119.3 mitogenomes.The libraries were screened with 28 markers derived from the conservative sequences and yielded 22,19,26,21,and 23 positive clones,respectively.These positive clones were used to construct the physical map of G.harknessii Brandegee.CMS line and G.barbadense L.mitogenomes that shared six syntenis regions.A total of 30 genes in nine clusters showed conservative and had high similarity with those in the mitochondrial genomes of cotton,Carica papaya,Cucurbita pepo and Nicotiana tabacum.Further investigation indicated that gene rrn26 had two copies in all five cotton mitogenomes,while genes atp1,rrn5 and rrn18 had two copies only in G.barbadense L.The positive clones and physical map are considered being useful resources in cotton genomics research.
LI ShuangShuangLIU GuoZhengCHEN ZhiWenWANG YuMeiLI PengBoHUA JinPing
With the development in spinning technology, the improvement of cotton fiber quality is becoming more and more important. The main objective of this research was to construct a high-density genetic linkage map to facilitate marker assisted selection for fiber quality traits in upland cotton (Gossypium hirsutum L.). A genetic linkage map comprising 421 loci and covering 3814.3 cM, accounting for approximately 73.35% of the cotton genome, was constructed using an F2 population derived from cross GX1135 (P 1 )×GX100-2 (P 2 ). Forty-four of 49 linkage groups were assigned to the 26 chromosomes. Fiber quality traits were investigated in F2 population sampled from individuals, and in F2:3 , and F2:4 generations sampled by lines from two sites and one respectively, and each followed a randomized complete block design with two replications. Thirty-nine quantitative trait loci were detected for five fiber quality traits with data from single environments (separate analysis each): 12 for fiber length, five for fiber uniformity, nine for fiber strength, seven for fiber elongation, and six for fiber micronaire, whereas 15 QTLs were found in combined analysis (data from means of different environments in F2:3 generation). Among these QTLs, qFL-chr5-2 and qFL-chr14-2 for fiber length were detected simultaneously in three generations (four environments) and verified further by combined analysis, and these QTLs should be useful for marker assisted selection to improve fiber quality in upland cotton.
