Genomic Insights into ARR Genes: Key Role in Cotton Leaf Abscission Formation

The cytokinin response regulator (<i>ARR</i>) gene is essential for cytokinin signal transduction, which plays a crucial role in plant growth and development. However, the functional mechanism of <i>ARR</i> genes in cotton leaf abscission remains incompletely understood. In this study, a total of 86 <i>ARR</i> genes were identified within the genome of <i>Gossypium hirsutum</i>. These genes were categorized into four distinct groups based on their phylogenetic characteristics, supported by analyses of gene structures and conserved protein motifs. The <i>GhARR</i> genes exhibited an uneven distribution across 25 chromosomes, with three pairs of tandem duplication events observed. Both segmental and tandem duplication events significantly contributed to the expansion of the <i>ARR</i> gene family. Furthermore, numerous putative cis-elements were identified in the promoter regions, with hormone and stress-related elements being common among all 86 <i>GhARR</i>s. Transcriptome expression profiling screening results demonstrated that <i>GhARR</i>s may play a mediating role in cotton's response to TDZ (<i>thidiazuron</i>). The functional validation of <i>GhARR16</i>, <i>GhARR43</i>, and <i>GhARR85</i> using virus-induced gene silencing (VIGS) technology demonstrated that the silencing of these genes led to pronounced leaf wilting and chlorosis in plants, accompanied by a substantial decrease in petiole fracture force. Overall, our study represents a comprehensive analysis of the <i>G. hirsutum ARR</i> gene family, revealing their potential roles in leaf abscission regulation.