Ectopic Overexpression of Domestication-Driven Cytoskeletal Profilin (GhPRF1) Gene Improves Flowering and Trichome Development in Cotton (Gossypium hirsutum L.)

Cotton, as a natural fiber crop, plays a pivotal role in advancing global textile industry. Comparative transcriptome analyses of single-cell ‘fiber’ from wild and domesticated plant revealed the evolutionary selection of cell wall-associated profilin gene family during cotton domestication. However, the evolutionary significance of elevated transcript abundance of profilins (GhPRFs) in floral and fiber tissues, and their practical application in the field for improving crop yield remain poorly understood. In this study, the domestication-driven 402 bp long GhPRF1 gene (Pro35Sde:GhPRF1-pA) was constitutively overexpressed in cotton (Gossypium hirsutum L. cv. Coker 310FR) through Agrobacterium-mediated genetic transformation of 1513 cotyledonary explants undergoing somatic embryogenesis. Out of the 32 putative GhPRF1 transgenic overexpression (Ox) lines produced, 26 lines were successfully confirmed with independent transgene integrations. Compared with those of the untransformed wild type (WT), the cumulative abundance of GhPRF1 transcripts in the leaf tissues of GhPRF1 overexpressing lines Pf-CaOx7, Pf-CaOx14, and Pf-CaOx19 substantially increased (> 12-fold). These transgenic lines exhibited increased numbers of secondary branches, flower buds per branch, and trichome density on the abaxial surface of leaves compared to the WT plants. Despite comparable fiber lengths between the overexpression lines and the WT, the enhanced fiber yields in the overexpression lines were attributed to increased flower number and boll production per branch. Remarkably, GhPRF1 overexpression also manifested transcriptional biases specific to profilin homologs in vegetative, floral, and fiber tissues. This is primarily attributed to increased actin polymerization and the formation of dense F-actin bundles, which are especially evident in the vascular regions of overexpression lines compared to those of the WT. This study revealed novel phenotypic and genetic foundations influencing floral and fiber architecture in cotton and offers promising avenues for manipulating agronomic traits.