Identification of ARF transcription factor gene family and its defense responses to bacterial infection and salicylic acid treatment in sugarcane.

Auxin response factor (ARF) is a critical regulator in the auxin signaling pathway, involved in a variety of plant biological processes. Here, gene members of 24 and 39 were identified in two genomes of clones AP85-441 and Np-X, respectively. Phylogenetic analysis showed that all genes were clustered into four clades, which is identical to those genes in maize () and sorghum (). The gene structure and domain composition of this ARF family are conserved to a large degree across plant species. The and genes were unevenly distributed on chromosomes 1-8 and 1-10 in the two genomes of AP85-441 and Np-X, respectively. Segmental duplication events may also contribute to this gene family expansion in . The post-transcriptional regulation of genes likely involves sugarcane against various stressors through a miRNA-medicated pathway. Expression levels of six representative genes were analyzed by qRT-PCR assays on two sugarcane cultivars [LCP85-384 (resistant to leaf scald) and ROC20 (susceptible to leaf scald)] triggered by subsp. () and () infections and salicylic acid (SA) treatment. functioned as a positive regulator under and stress, whereas it was a negative regulator under SA treatment. genes played positive roles against both pathogenic bacteria and SA stresses. Additionally, was negatively modulated by and stimuli in both cultivars, particularly LCP85-384. These findings imply that sugarcane exhibit functional redundancy and divergence against stressful conditions. This work lays the foundation for further research on gene functions in sugarcane against diverse environmental stressors.