The U-box family genes in Medicago truncatula: Key elements in response to salt, cold, and drought stresses

• DOI: 10.1371/journal.pone.0182402
• Publication Date: 2017-08-03T14:05:08Z
• Authors: Jianbo Song; Xiaowei Mo; Haiqi Yang; Luming Yue; Jun Song; Beixin Mo
• Keywords: 0301 basic medicine; 2. Zero hunger; Science; Gene Expression Profiling; Ubiquitin-Protein Ligases; Q; R; Salt Tolerance; 15. Life on land; Chromosomes, Plant; 6. Clean water; Droughts; Cold Temperature; 03 medical and health sciences; Gene Expression Regulation, Plant; Stress, Physiological; Multigene Family; Medicago truncatula; Medicine; Research Article; Plant Proteins

The ubiquitination pathway regulates growth, development, and stress responses in plants, and the U-box protein family of ubiquitin ligases has important roles in this pathway. Here, 64 putative U-box proteins were identified in the Medicago truncatula genome. In addition to the conserved U-box motif, other functional domains, such as the ARM, kinase, KAP, and WD40 domains, were also detected. Phylogenetic analysis of the M. truncatula U-box proteins grouped them into six subfamilies, and chromosomal mapping and synteny analyses indicated that tandem and segmental duplications may have contributed to the expansion and evolution of the U-box gene family in this species. Using RNA-seq data from M. truncatula seedlings subjected to three different abiotic stresses, we identified 33 stress-inducible plant U-box genes (MtPUBs). Specifically, 25 salinity-, 15 drought-, and 16 cold-regulated MtPUBs were detected. Among them, MtPUB10, MtPUB17, MtPUB18, MtPUB35, MtPUB42, and MtPUB44 responded to all three stress conditions. Expression profiling by qRT-PCR was consistent with the RNA-seq data, and stress-related elements were identified in the promoter regions. The present findings strongly indicate that U-box proteins play critical roles in abiotic stress response in M. truncatula.