Abstract
Melilotus albus is an annual or biennial legume species that adapts to extreme environments via its high stress tolerance. NAC and MYB transcription factors (TFs) are involved in the regulation of lignin biosynthesis, which has not been studied in M. albus. A total of 101 MaNAC and 299 MaMYB members were identified based on M. albus genome. Chromosome distribution and synteny analysis indicated that some genes underwent tandem duplication. Ka/Ks analysis suggested that MaNACs and MaMYBs underwent strong purifying selection. Stress-, hormone- and development-related cis-elements and MYB-binding sites were identified in the promoter regions of MaNACs and MaMYBs. Five MaNACs, two MaMYBs and ten lignin biosynthesis genes were identified as presenting coexpression relationships according to weighted gene coexpression network analysis (WGCNA). Eleven and thirteen candidate MaNAC and MaMYB genes related to lignin biosynthesis were identified, respectively, and a network comprising these genes was constructed which further confirmed the MaNAC and MaMYB relationship. These candidate genes had conserved gene structures and motifs and were highly expressed in the stems and roots, and qRT-PCR further verified the expression patterns. Overall, our results provide a reference for determining the precise role of NAC and MYB genes in M. albus and may facilitate efforts to breed low-lignin-content forage cultivars in the future.
Highlights
IntroductionNAC (no apical meristem (NAM), Arabidopsis transcription activation factor (ATAF1/2), and cup-shaped cotyledon (CUC2)) family members are plant-specific transcription factors (TFs). NAC TFs have a highly conserved N-terminal region and a variable C-terminal region; the N-terminal regions share a conserved DNA-binding region, whereas the C-terminal regions have various transcriptional regulatory domains [1,2,3]
Received: 21 September 2020Transcription factors (TFs) play an important role in plant growth and development.NAC (no apical meristem (NAM), Arabidopsis transcription activation factor (ATAF1/2), and cup-shaped cotyledon (CUC2)) family members are plant-specific transcription factors (TFs)
A total of 101 MaNAC and 299 MaMYB family members were identified in M. albus
Summary
NAC (no apical meristem (NAM), Arabidopsis transcription activation factor (ATAF1/2), and cup-shaped cotyledon (CUC2)) family members are plant-specific TFs. NAC TFs have a highly conserved N-terminal region and a variable C-terminal region; the N-terminal regions share a conserved DNA-binding region, whereas the C-terminal regions have various transcriptional regulatory domains [1,2,3]. NAC proteins has α-helical transmembrane motifs that are related to stress responses [4,5]. These features help these proteins repress or activate various downstream genes to regulate multiple molecular or cellular processes. NAC proteins are involved in the regulation of various biological functions. ATAF1, which encodes an NAC TF, is a stimulus-dependent attenuator of abscisic acid signaling involved in mediating penetration resistance [7]
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