Root-Growth-Related MaTCP Transcription Factors Responsive to Drought Stress in Mulberry

Root growth regulation plays a crucial role in the acclimatization of plants to their surroundings, but the molecular mechanisms underlying this process remain largely uncertain. Teosinte branched1/cycloidea/proliferating cell factor (TCP) transcription factors are crucial elements linking together plant growth and development, phytohormone signaling, and stress response. In this study, 15 TCP transcription factors were identified in the mulberry (Morus alba) genome. Gene structure, conserved motif, and phylogenetic analyses revealed the conservation and divergence of these MaTCPs, thus providing insights into their functions. A promoter analysis uncovered distinct numbers and compositions of cis-elements in MaTCP gene promoter regions that may be connected to reproductive growth and phytohormone and stress responses. An expression pattern analysis of the 15 MaTCP genes in mulberry roots indicated that transcriptional levels of MaTCP2, MaTCP4-1, MaTCP8, MaTCP9-1, and MaTCP20-2 are correlated with root development. As revealed by changes in their expressions after drought treatment, these five MaTCP genes are involved in root growth and may increase mulberry tolerance to drought. Our findings lay the foundation for future functional studies of these genes.