Use of Arabidopsis to Test the Function of Cotton Orthologous Genes

Recent studies indicate that Arabidopsis cDNA are closely related to that of Gossypium species. Cotton seed-specific promoters work well in Arabidopsis and tobacco (Sunilkumar et al., 2002; Kim and Triplett, 2001). Reporter constructs using a G. hirsutum cellulose synthase promoter showed tissue-specific expression patterns identical to those of Arabidopsis cellulose synthases producing secondary cell wall (Doblin et al., 2001; Holland et al., 2000). Notably, over-expression of Antirrhinum MIXTA (a Myb gene) complements conical cell formation in tobacco leaves (Glover et al., 1998; Noda et al., 1994). Expression of cotton GaMYB2 in Arabidopsis by GL1::GaMYB2 complemented trichome development in the glabrous 1 mutant. Furthermore, over-expression of cotton GaMYB2 induced seed trichome formation in Arabidopsis (Wang et al. 2004). The first intron contained critical element for trichome specific expression (Wang et al. 2004).

In transgenic Arabidopsis, GUS activity (blue color) regulated by the GhCesA4 promoter was specifically expressed in leaf hair cells as GhCesA4 is specifically expressed in cotton fiber hair cells (Figure). Using the transgenic Arabidopsis, we discovered that the promoter of GhCesA4 developmentally regulated during both cotton fiber and Arabidopsis hair cell developments and that auxin, one of plant hormone, was involved in cellulose production.