Genome-wide identification of <i>SMALL AUXIN UP RNA (SAUR)</i> gene family and its expression profiles in response to abiotic stress and auxin in tea plants ( <i>Camellia sinensis</i> )

Tea plant (<i>Camellia sinensis</i> (L.) O. Kuntze) is particularly vulnerable to abiotic stresses, with impacts on its growth and the production of bioactive compounds. <i>SMALL AUXIN UP RNA (SAUR)</i> genes, the largest family of early auxin-responsive genes, regulate plant growth and abiotic stress responses. However, their roles in tea plant remain unknown. In this study, we conducted a comprehensive genome-wide analysis of <i>CsSAURs</i>, including phylogenetic relationships, gene structure, chromosomal distribution, duplication events, motif composition, <i>cis</i>-elements, and gene ontology (GO) annotations. Expression profiles were examined using transcriptome data and validated by qRT-PCR. A total of 97 <i>CsSAURs</i> were identified and classified into eight phylogenetic groups, with 90 mapped to 15 chromosomes and seven to contigs. Genes within the same group exhibit conserved gene structures and motif compositions. Segmental duplication predominantly contributes to family expansion. The predominant <i>CsSAUR</i> expression was found in flowers, with their promoters containing auxin-responsive, phytohormone, and stress-related <i>cis</i>-elements. A limited number of <i>CsSAURs</i> exhibit responsiveness to cold, drought, salinity, and methyl jasmonate (MeJA). Notably, <i>CsSAUR10</i>, <i>16</i>, and <i>73</i> exhibited significant upregulation under abiotic stress and auxin treatment. Overall, this study characterizes the <i>SAUR</i> family in tea plant and highlights its potential roles in the regulation of growth and stress responses. The identified auxin and stress-responsive <i>CsSAURs</i> represent potential targets for genetic improvement of tea plants.