Abstract
Plant CIRCADIAN CLOCK ASSOCIATED1 (CCA1)-like proteins are a class of single-repeat MYELOBLASTOSIS ONCOGENE (MYB) transcription factors generally featured by a highly conserved motif SHAQK(Y/F)F, which play important roles in multiple biological processes. Soybean is an important grain legume for seed protein and edible vegetable oil. However, essential understandings regarding CCA1-like proteins are very limited in soybean. In this study, 54 CCA1-like proteins were identified by data mining of soybean genome. Phylogenetic analysis indicated that soybean CCA1-like subfamily showed evolutionary conservation and diversification. These CCA1-like genes displayed tissue-specific expression patterns, and analysis of genomic organization and evolution revealed 23 duplicated gene pairs. Among them, GmMYB138a was chosen for further investigation. Our protein–protein interaction studies revealed that GmMYB138a, but not its alternatively spliced isoform, interacts with a 14-3-3 protein (GmSGF14l). Although GmMYB138a was predominately localized in nucleus, the resulting complex of GmMYB138a and GmSGF14l was almost evenly distributed in nucleus and cytoplasm, supporting that 14-3-3s interact with their clients to alter their subcellular localization. Additionally, qPCR analysis suggested that GmMYB138a and GmSGF14l synergistically or antagonistically respond to drought, cold and salt stresses. Our findings will contribute to future research in regard to functions of soybean CCA1-like subfamily, especially regulatory mechanisms of GmMYB138a in response to abiotic stresses.
Highlights
MYB (MYELOBLASTOSIS ONCOGENE) transcription factors are a class of key players in the regulatory networks underlying plant growth and development as well as plant responses to stresses
LHY and CLOCK ASSOCIATED1 (CCA1) regulate photoperiodic flowering via affecting expression of FT gene in Arabidopsis [12,13]; MYBD and RVE8/LCL5 function as positive regulators to be involved in the regulation of anthocyanin biosynthesis [17,18]; RVE1/2 can control seed dormancy and germination [19]; MYBH participates in the regulation of leaf senescence [20]; CCA1 regulates ROS (Reactive oxygen species) homeostasis and oxidative stress responses [11]; and OsMYBS3 (MYB-RELATED PROTEIN S3) is essential for cold adaptation in rice [21]
CCA1-like proteins might localize in nucleus, they still have potential to be targeted to other organelles such as cytoplasm, peroxisome, chloroplast and/or mitochondria (Table S1)
Summary
MYB (MYELOBLASTOSIS ONCOGENE) transcription factors are a class of key players in the regulatory networks underlying plant growth and development as well as plant responses to stresses. In addition to the involvement of circadian rhythm regulation, increasing evidence indicated that CCA1-like proteins might perform diverse functions in various biological processes including the biosynthesis of isoflavonoid and anthocyanin, flowering, leaf senescence, hypocotyl elongation, seed germination, hormone signaling pathway, and stress responses [10,11,12,13,14,15,16]. LHY and CCA1 regulate photoperiodic flowering via affecting expression of FT gene in Arabidopsis [12,13]; MYBD and RVE8/LCL5 function as positive regulators to be involved in the regulation of anthocyanin biosynthesis [17,18]; RVE1/2 can control seed dormancy and germination [19]; MYBH participates in the regulation of leaf senescence [20]; CCA1 regulates ROS (Reactive oxygen species) homeostasis and oxidative stress responses [11]; and OsMYBS3 (MYB-RELATED PROTEIN S3) is essential for cold adaptation in rice [21]. Identification and characterization of CCA1-like proteins in diverse plant species becomes an important step toward understanding their functional roles
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