Polyploidization-driven formation of the <i>GhRALF30L</i> gene cluster confers basal thermotolerance in cotton male reproductive organs via <i>GhFERA1</i> / <i>GhCAPA1</i>

High-temperature stress in plant stamens frequently causes male sterility, limiting crop yields. Gene duplication resulting from polyploidization offers insights into plant adaptation to environmental stress. Here, we reveal that extensive duplication of <i>GhRALF30L</i>, which encodes an intrinsically disordered small peptide, contributes to thermotolerance in cotton male reproductive organs. Polyploidization has driven the formation of 23 <i>GhRALF30L</i> genes in allotetraploid cotton, whereas only four or five homologs are identified in its two diploid ancestors. Expression and functional analyses confirm that <i>GhRALF30L</i> regulates thermotolerance in a dosage-dependent manner, with reduced dosage decreasing heat resistance. Under heat stress, GhRALF30L interacts with GhFERA1/GhCAPA1 and enhances their condensation at the plasma membrane, which activates heat stress responses by up-regulating the expression of heat shock factors (<i>HSFs</i>), heat shock proteins (<i>HSPs</i>), and reactive oxygen species scavenging genes. Our findings demonstrate that the <i>GhRALF30L</i> gene cluster, resulting from polyploidization, confers thermotolerance through facilitating the condensation of GhFERA1/GhCAPA1.