A full-length normalized cDNA library for the flower development stages of short-season cotton （Gossypium hirsutum L.） （CCRI36） was constructed. A total of 3 421 clones were randomly selected for sequencing, with a total of 3 175 effective sequences obtained after removal of empty-carriers and low-quality sequences. Clustering the 3 175 high-quality expressed sequence tags （ESTs） resulted in a set of 2 906 non-redundant sequences comprised of 233 contigs and 2 673 singletons. Comparative analyses indicated that 913 （43.6%） of the unigenes had homologues with function-known genes or functionassumed genes in the National Center for Biotechnology Information. In addition, 763 （36.4%） of the unigenes were functionally classified using Gene Ontology hierarchy. Through EST alignment and the screening method, the full-length cDNA of two MADS-box genes viz., GhMADSll and GhMADS12 were acquired. These genes may play a role in flower development. Phylogenetie analysis indicated that GhMADS11 and GhMADS12 had high homology and close evolutionary relationship with AGL2/SEP-type and PI-type genes, respectively. The expression of both GhMADSll and GhMADS12, genes was high in reproductive organs. In floral organs, GhMADSll expression was high in petals （whor12） and ovules, while GhMADS12 expression was high in petals （whor12） and stamens （whor13）. Results show that the EST strategy based on a normalized cDNA library is an effective method for gene identification. The study provides more insights for future molecular research on the regulation mechanism of cotton flower development.
WANG Li-na WU Dong YU Shu-xun FAN Shu-li SONG Mei-zhen PANG Chao-you LIU Jun-jie
The study aims to clarify the differential gene expression between cotton hybrids and their parents in order to better understand the molecular basis of cotton heterosis. The research focused on cotton heterotic and lower heterotic hybrids and their parents during the four crucial stages, which were analyzed using a differential display technique. The results indicated that there were both quantitative and qualitative differences in gene expression amongst them. The quantitative differences include over- and under-expression of parental genes and the dominant expression of highly-expressed parental genes in hybrids. In contrast, the qualitative differences are the following： （i） Bands were observed in both parents but not in the F1 hybrid （BPnF1）; （ii） bands occurred in either of the parents but not in the F1 hybrid （UPnF1）; （iii） bands presented only in the F1 hybrid but not in either of the parents （UF1nP）; and （iv） bands were detected in either of the parents and the F1 hybrid （UPF1）. Overall, the major differences of gene expression occurred in the qualitative level and four related differential patterns were observed. Furthermore, the amount of differential patterns during the flowering stage was relatively higher than those of other stages. At this juncture, both the amount of hybrid-specific expression patterns at flowering stage and the silenced expression patterns at boll-forming stage in highly heterotic hybrids were found higher than those in the lower heterotic ones. It was concluded that significant differences of gene expression in leaves were present between cotton hybrid and its parents during the whole growing stages. Hence, these differences might be responsible for the observed cotton heterosis.
ZHAO Yun-lei, YU Shu-xun, XING Chao-zhu, FAN Shu-li, SONG Mei-zhen and YE Wu-wei Cotton Research Institute, Chinese Academy of Agricultural Sciences(CAAS)/Key Laboratory of Cotton Genetic Improvement, Ministry of Agriculture, Anyang 455000, P.R.China
