Genome-Wide Characterization, Evolutionary Analysis of <i>ARF</i> Gene Family, and the Role of <i>SaARF4</i> in Cd Accumulation of <i>Sedum alfredii</i> Hance

Auxin response factors (<i>ARFs</i>) play important roles in plant development and environmental adaption. However, the function of <i>ARFs</i> in cadmium (Cd) accumulation are still unknown. Here, 23 <i>SaARFs</i> were detected in the genome of hyperaccumulating ecotype of <i>Sedum alfredii</i> Hance (HE), and they were not evenly distributed on the chromosomes. Their protein domains remained highly conservative. <i>SaARFs</i> in the phylogenetic tree can be divided into three groups. Genes in the group Ⅰ contained three introns at most. However, over ten introns were found in other two groups. Collinearity relationships were exhibited among ten <i>SaARFs</i>. The reasons for generating <i>SaARFs</i> may be segmental duplication and rearrangements. Collinearity analysis among different species revealed that more collinear genes of <i>SaARFs</i> can be found in the species with close relationships of HE. A total of eight elements in <i>SaARFs</i> promoters were related with abiotic stress. The qRT-PCR results indicated that four <i>SaARFs</i> can respond to Cd stress. Moreover, that there may be functional redundancy among six <i>SaARFs</i>. The adaptive selection and functional divergence analysis indicated that <i>SaARF4</i> may undergo positive selection pressure and an adaptive-evolution process. Overexpressing <i>SaARF4</i> effectively declined Cd accumulation. Eleven single nucleotide polymorphism (SNP) sites relevant to Cd accumulation can be detected in <i>SaARF4</i>. Among them, only one SNP site can alter the sequence of the <i>SaARF4</i> protein, but the <i>SaARF4</i> mutant of this site did not cause a significant difference in cadmium content, compared with wild-type plants. <i>SaARFs</i> may be involved in Cd-stress responses, and <i>SaARF4</i> may be applied for decreasing Cd accumulation of plants.