Abstract
The two-component signal transduction system (TCS) acts in a variety of physiological processes in lower organisms and has emerged as a key signaling system in both prokaryotes and eukaryotes, including plants. TCS genes assist plants in processes such as stress resistance, cell division, nutrition signaling, leaf senescence, and chloroplast division. In plants, this system is composed of three types of proteins: response regulators (RRs), histidine kinases (HKs), and histidine phosphotransfer proteins (HPs). We aimed to study the Sorghum bicolor genome and identified 37 SbTCS genes consisting of 13 HKs, 5 HPs, and 19 RRs (3 type-A RRs, 7 type-B RRs, 2 type-C RRs, and 7 pseudo-RRs). The structural and phylogenetic comparison of the SbTCS members with their counterparts in Arabidopsis thaliana, Oryza sativa, Cicer arietinum, and Glycine max showed group-specific conservations and variations. Expansion of the gene family members is mostly a result of gene duplication, of both the tandem and segmental types. HKs and RRs were observed to be originated from segmental duplication, while some HPs originated from tandem duplication. The nuclear genome of S. bicolor contain 10 chromosomes and these SbTCS genes are randomly distributed on all the chromosomes. The promoter sequences of the SbTCS genes contain several abiotic stress-related cis-elements. RNA-seq and qRT-PCR-based expression analysis demonstrated most of the TCS genes were responsive to drought and salt stresses in leaves, which suggest their role in leaf development. This study lays a foundation for further functional study of TCS genes for stress tolerance and developmental improvement in S. bicolor.
Highlights
The two-component system (TCS) was first recognized in bacteria, and it has since been studied for signal transduction pathways in fungi, slime molds, and plants (Stock et al, 2000)
A BLASTp search was performed to identify the putative members of the transduction system (TCS) gene family in S. bicolor by employing 47 A. thaliana TCS query protein sequences
A total of 37 TCS genes were identified in the genome of S. bicolor, which were further divided into 13 histidine kinases (HKs), 5 histidine phosphotransfer proteins (HPs), and 19 RRs
Summary
The two-component system (TCS) was first recognized in bacteria, and it has since been studied for signal transduction pathways in fungi, slime molds, and plants (Stock et al, 2000). In the receiver domain of the RR (Rec), the phosphate group is transferred to a conserved Asp residue (Aspartic acid) Another domain, known as the output domain, is found in many RRs; its activity is regulated by the phosphorylation state of the Rec domain whereas, Rec domain is a response regulator receiver domain. In the corresponding signaling cascade, a phosphate group is transferred among the HP family members, and may involve as a linker between HKs and RRs proteins (Wurgler-murphy 1997; West et al, 2001). In plants such as Arabidopsis thaliana, there are three distinct subfamilies of HKs: ethylene receptor, phytochrome receptor, and cytokinin receptors (Hwang et al, 2002). AHK2, AHK3, and AHK4 are considered cytokinin receptors, which are recognized on the basis of containing the cyclase/HK-associated sensing extracellular (CHASE) domain (Hutchison and Kieber, 2002)
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