Abstract
Calmodulin-binding transcription activators (CAMTAs) are well-characterized calmodulin-binding transcription factors in the plant kingdom. Previous work shows that CAMTAs play important roles in various biological processes including disease resistance, herbivore attack response, and abiotic stress tolerance. However, studies that address the function of CAMTAs during the establishment of symbiosis between legumes and rhizobia are still lacking. This study undertook comprehensive identification and analysis of CAMTA genes using the latest updated M. truncatula genome. All the MtCAMTA genes were expressed in a tissues-specific manner and were responsive to environmental stress-related hormones. The expression profiling of MtCAMTA genes during the early phase of Sinorhizobium meliloti infection was also analyzed. Our data showed that the expression of most MtCAMTA genes was suppressed in roots by S. meliloti infection. The responsiveness of MtCAMTAs to S. meliloti infection indicated that they may function as calcium-regulated transcription factors in the early nodulation signaling pathway. In addition, bioinformatics analysis showed that CAMTA binding sites existed in the promoter regions of various early rhizobial infection response genes, suggesting possible MtCAMTAs-regulated downstream candidate genes during the early phase of S. meliloti infection. Taken together, these results provide basic information about MtCAMTAs in the model legume M. truncatula, and the involvement of MtCAMTAs in nodule organogenesis. This information furthers our understanding of MtCAMTA protein functions in M. truncatula and opens new avenues for continued research.
Highlights
Ca2+ signals are core transducers and regulators in many adaptive and developmental plant processes (Kudla et al, 2010)
Genome-wide Identification of Calmodulin-binding transcription activators (CAMTAs) Genes in M. truncatula A total of seven putative MtCAMTA genes were identified at the phytozome website
To date there are still no studies on CAMTAs in M. truncatula, an important leguminous model plant that is widely used in symbiosis research
Summary
Ca2+ signals are core transducers and regulators in many adaptive and developmental plant processes (Kudla et al, 2010). Calmodulin is the best characterized Ca2+ binding protein whose role relies on its ability to physically bind to a large population of target proteins, including protein kinases, phosphatases, transcription factors, metabolic enzymes, ion channels, transporters, and molecular motors (Yang and Poovaiah, 2003; Bouche’ et al, 2005; Du et al, 2011; Poovaiah et al, 2013). Ca2+/calmodulin binds to CAMTAs’ CaM binding domain, and this binding regulates the activity of CAMTAs as transcriptional factors (Bouche’ et al, 2002; Yang and Poovaiah, 2002; Choi et al, 2005; Du et al, 2009). The CAMTAs can recognize and bind to (A/C/G)CGCG(T/C/G) or (A/C)CGTGT DNA cis-element in the promoter regions of downstream genes, which results in the regulation of gene expression (Yang and Poovaiah, 2002; Choi et al, 2005)
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