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Cotton fiber strength is mainly determined during the secondary cell wall (SCW) thickening stage. In 24?25 days post anthesis (DPA) of SCW thickening stage, cDNA-amplified fragment length polymorphism (AFLP) was carried out to construct fiber transcriptome groups. Based on these groups, cotton fiber strength candidate genes were detected by composite interval mapping (CIM) through quantitative trait locus (QTL) scanning. The mapping population was the interspecific backcross BC1 of Gossypium hirsutum × G. barbadense. One hundred and fifteen BC1 plants were used for group construction with 102 qualified absence/presence polymorphic transcript-derived fragments (TDFs) from G. barbadense, and 78 TDFs were assigned into eight transcriptome groups that gave a total length of 462.63 centimorgans (cM). Two significant QTLs, FS1 and FS2, were detected and explained 16.08% and 15.87% of fiber strength variance, respectively. Of the six TDFs co-segregating with FS1 and FS2, except one encoding an unknown protein, five targeted putative phosphatidylinositol kinase, trehalose-6-phosphate synthase, MADS transcription factor, cellulose synthase-like protein and phenylalanine ammonia lyase, respectively. These functional genes were involved in plant cell wall morphogenesis or cellulose synthesis metabolism processes, and were considered as the candidate genes controlling cotton fiber strength. [ABSTRACT FROM AUTHOR]

The continuous growth of lowland rice (LR) in paddy fields supplied with enough water over the years, and of upland rice (UR) in naturally rain-fed soils, has resulted in greater resistance to drought stress in UR compared to LR. To elucidate their differential regulation mechanisms of drought-resistance, genome- wide transcript regulation under drought stress in UR and LR was investigated using cDNA-AFLP. The results indicated that over 90% of gene expression was not affected by drought stress in the two rice genotypes, more than 8% was regulated by drought stress in both, and less than 1% was specifically expressed in UR or LR. Fifty-seven genes were specifically expressed in UR and thirty-eight specifically in LR. Genes specifically expressed in UR included cell rescue and defence genes functioning in drought-resistance, signal transduction molecules, nucleotides and amino acid biosynthesis genes required for plant growth, and the regulatory genes for growth and development. In LR, genes specifically expressed were related to protein and nucleotide degradation. Some genes were upregulated earlier in UR, and downregulated genes were inclined to be downregulated earlier in UR compared to LR, implying that more rapid regulation mechanisms caused earlier responses of UR to drought stress. Expression levels of upregulated genes in UR were higher than those in LR. The differences in gene expression between UR and LR could account for stronger regulation ability, more drought-resistance and superior growth of UR under drought stress compared to LR. [ABSTRACT FROM AUTHOR]

Cotton fiber strength is mainly determined during the secondary cell wall deposition stage when cellulose is synthesized. We obtained cDNA of 20-25 d post anthesis (DPA) fiber from 109 F2 progeny and developed a cotton fiber transcriptome profiling via cDNA-AFLP technology using 37 different primer combinations. The F2 population originated from an interspecific cross between Gossypium hirsutum and Gossypium barbadense. One hundred and thirty-eight absence/presence polymorphic transcript- derived fragments (TDFs), with sizes ranging from 100 bp to 722 bp, were screened. Of these, 75 (53.62%) were polymorphic between the parents of the F2 population. Sequencing the 75 transcripts revealed that 37 of them had been reported to be cotton fiber ESTs. Nine of 75 transcript sequences were homologous to 7 cloned cotton fiber genes, encoding cysteine proteinase, vacuolar H+-pyrophosphatase, vacuolar H+-ATPase, catalytic subunit, arabinogalactan protein, putative receptor protein kinase PERK1, GIA/RGA-like gibberellin response modulator and cellulose synthase. Some other transcripts may represent new gene fragments in cotton fiber development. Surprisingly, 46 of the 75 transcripts were mapped to a single linkage group. The transcriptome groups and the sequenced TDF5 could serve as important resources in the functional genomic research of cotton fiber development. [ABSTRACT FROM AUTHOR]