Abstract
The two-component system (TCS), which comprises histidine kinases (HKs), phosphotransfers (HPs), and response regulator proteins (RRs), plays pivotal roles in regulating plant growth, development, and responses to biotic and abiotic stresses. TCS genes have been comprehensively identified and investigated in various crops but poorly characterized in tomato. In this work, a total of 65 TCS genes consisting of 20 HK(L)s, six HPs, and 39 RRs were identified from tomato genome. The classification, gene structures, conserved domains, chromosome distribution, phylogenetic relationship, gene duplication events, and subcellular localization of the TCS gene family were predicted and analyzed in detail. The amino acid sequences of tomato TCS family members, except those of type-B RRs, are highly conserved. The gene duplication events of the TCS family mainly occurred in the RR family. Furthermore, the expansion of RRs was attributed to both segment and tandem duplication. The subcellular localizations of the selected green fluorescent protein (GFP) fusion proteins exhibited a diverse subcellular targeting, thereby confirming their predicted divergent functionality. The majority of TCS family members showed distinct organ- or development-specific expression patterns. In addition, most of TCS genes were induced by abiotic stresses and exogenous phytohormones. The full elucidation of TCS elements will be helpful for comprehensive analysis of the molecular biology and physiological role of the TCS superfamily.
Highlights
A two-component system (TCS) via phosphorylation between histidine and aspartic-acid residues was first identified in bacteria [1,2]
65 TCS members consisting of 20 histidine kinases (HKs)(L)s, six histidine-containing phosphotransfers (HPs), and 39 regulator proteins (RRs) were confirmed in tomato
All tomato TCS members were named according to the homologous genes in Arabidopsis
Summary
A two-component system (TCS) via phosphorylation between histidine and aspartic-acid residues was first identified in bacteria [1,2]. AHK2, AHK3, and AHK4 function as cytokinin receptors and negatively respond to stresses in Arabidopsis cytokinin signaling [3,4,5,6]. These kinases perceive stimulus and are autophosphorylated at a conserved histidine residue in transmitter domain. HPs transmit the signal to receiver domain in type-B RRs, which could function as transcription factor to response to various environmental signals via numerous cis-elements in the promoter of type-A ARRs and further regulate the expression of downstream stress-related genes [3,4,5,6]
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