GhH2A12, a replication-dependent histone H2A gene from Gossypium hirsutum, is negatively involved in the development of cotton fiber cells

GhH2A12 was preferentially expressed at the initiation and early elongation stage of cotton fiber development, and overexpression of GhH2A12 caused retardation of fiber initiation and produced shorter fibers. Histone H2A is a component of eukaryotic chromatin whose function has not been studied in cotton. We have isolated an H2A gene encoding 156 amino acids, named GhH2A12. Like other plant histone H2As, GhH2A12 contains a typical SPKK motif in the carboxy-terminal and a plant-unique peptide-binding A/T-rich DNA region, and it was localized to the nucleus. GhH2A12 was preferentially expressed at the initiation and early elongation stage of cotton fiber, from 0 to 5 days post anthesis and the transcript level declined rapidly when the fiber entered the fast elongation stage, suggesting that GhH2A12 was involved in fiber differentiation. Therefore, GhH2A12 overexpression and RNAi transgenic cotton lines were developed via Agrobacterium tumefaciens-mediated transformation. Overexpression of GhH2A12 caused retardation of fiber initiation and produced shorter fibers and lower lint percentages. Moreover, the overexpressors showed negative effects on seedling growth, and the leaf emergence was delayed compared to wild type. However, no significant change in the GhH2A12 suppression line was observed. Coupled with retardation of fiber initiation, upregulation of GhH2A12 downregulated the expression of genes involved in cell-cycle performance. These results suggest that GhH2A12 might regulate fiber differentiation via regulating the cell cycle-related genes.