Overexpression of from Fine-Stem Stylo ( var. ) Enhances Chilling and Cold Tolerance in .

(stylo) species are commercially significant tropical and subtropical forage and pasture legumes that are vulnerable to chilling and frost. However, little is known about the molecular mechanisms behind stylos' responses to low temperature stress. Gretchen-Hagen 3 (GH3) proteins have been extensively investigated in many plant species for their roles in auxin homeostasis and abiotic stress responses, but none have been reported in stylos. , a cold-responsive gene identified in a whole transcriptome profiling study of fine-stem stylo ( var. ) was further investigated for its involvement in cold stress tolerance. shared a high percentage of identity with 14 leguminous GH3 proteins, ranging from 79% to 93%. Phylogenetic analysis classified SgGH3.1 into Group Ⅱ of GH3 family, which have been proven to involve with auxins conjugation. Expression profiling revealed that responded rapidly to cold stress in stylo leaves. Overexpression of in altered sensitivity to exogenous IAA, up-regulated transcription of genes, activated physiological responses against cold stress, and enhanced chilling and cold tolerances. This is the first report of a gene in stylos, which not only validated its function in IAA homeostasis and cold responses, but also gave insight into breeding of cold-tolerant stylos.