Genome-Wide Analysis of GRETCHEN HAGEN3 Genes and Characterization of IAA-Amido Synthetase Gene CsGH3.1 in Rhizome Proliferation in Cymbidium sinense ‘Qijianbaimo’

This study systematically identified and functionally analyzed the <i>GRETCHEN HAGEN</i> 3 (<i>GH3</i>) gene family in <i>Cymbidium sinense</i> 'Qijianbaimo' (CSQ). Seven <i>GH3</i> genes (<i>CsGH3.1</i>-<i>CsGH3.7</i>) were identified using genomic and transcriptomic data. Phylogenetic analysis revealed that CsGH3s are divided into two subfamilies, with CsGH3.1-CsGH3.4 belonging to subfamily II and CsGH3.5-CsGH3.7 to subfamily I. Gene structure analysis showed that <i>CsGH3s</i> contain one to four exons, and their promoter regions feature auxin and jasmonic acid response elements. <i>CsGH3.1</i> and <i>CsGH3.2</i> were significantly upregulated in response to naphthaleneacetic acid (NAA) during rhizome proliferation, indicating their pivotal role in auxin homeostasis regulation. The overexpression of <i>CsGH3.1</i> in <i>Arabidopsis</i> led to restricted growth and a significant reduction in callus proliferation rates, further confirming its role in regulating cell proliferation and auxin homeostasis. This study provides new insights into the function of the <i>CsGH3.1</i> gene in the rhizome proliferation of <i>Cymbidium sinense</i> and lays a foundation for future research on the molecular mechanism of micropropagation in <i>Cymbidium</i>.