EXPRESSION ANALYSIS OF GENES ASSOCIATED WITH SECONDARY CELL WALL BIOSYNTHESIS IN COTTON (Gossypium hirsutum L.)

Cotton the most important textile crop is grouped in to four cultivated species G. barbadense, G.hirsutum, G. herbaceum and G.arboreum. G. hirsutum is the most commonly grown worldwide and nearly 25 M tons bales of total cotton is produced annually. In India cotton is grown in 125.86 lakh hectare area and the production is 370 lakh bale in the year 2018/2019.Cotton fibers are single elongated cells originate from the epidermal layer and fiber initiation occurs on the day of anthesis, they rapidly elongate during 5-20 (days post anthesis) dpa normally. The onset of secondary cell wall biosynthesis typically occurs from 16-21 dpa depending on the cotton species and environmental conditions. The secondary cell wall biosynthesis overlaps by several days from fibre initiation to elongation; the maximum cell wall deposition takes place between 21-23 dpa. Expression of genes at each stage has its own distinctive regulatory features. In the present study, we selected major candidate genes viz., GhcesA1, GhcesA2 and GhcesA7 which are associated with secondary cell wall biosynthesis. The gene expression analysis of RILs mapping population revealed transcriptomic differences in low, medium and high fiber strength RILs at different fiber developmental stages. The gene expression data of qPCR analysis showed higher gene expression level in GhcesA1, GhcesA2, and GhcesA7 genes in the high fiber strength lines at 25, 30 dpa, whereas gene expression in low and medium fibre strength lines at all the fiber developmental stages. The cellulose synthase and 1,3- β -glucanase increases the secondary cell wall synthesis in cotton fibers. The study revealed that gene expression of GhcesA1, GhcesA2, GhcesA7 genes increased exponentially around 5–10 dpa, reaching a maximum at 15dpa-23dpa, coinciding with the increased cellulose accumulation.