Genome-Wide Identification, Structure Characterization, Expression Pattern Profiling, and Substrate Specificity of the Metal Tolerance Protein Family in Canavalia rosea (Sw.) DC.

Tao Zou,Ruoyi Lin,Mei Zhang,Qiming Mei,Shuguang Jian,Lin Pu,Zhengfeng Wang

doi:10.3390/plants10071340

Abstract

Plant metal tolerance proteins (MTPs) play key roles in heavy metal absorption and homeostasis in plants. By using genome-wide and phylogenetic approaches, the origin and diversification of MTPs from Canavalia rosea (Sw.) DC. was explored. Canavalia rosea (bay bean) is an extremophile halophyte with strong adaptability to seawater and drought and thereby shows specific metal tolerance with a potential phytoremediation ability. However, MTP genes in leguminous plants remain poorly understood. In our study, a total of 12 MTP genes were identified in C. rosea. Multiple sequence alignments showed that all CrMTP proteins possessed the conserved transmembrane domains (TM1 to TM6) and could be classified into three subfamilies: Zn-CDFs (five members), Fe/Zn-CDFs (five members), and Mn-CDFs (two members). Promoter cis-acting element analyses revealed that a distinct number and composition of heavy metal regulated elements and other stress-responsive elements existed in different promoter regions of CrMTPs. Analysis of transcriptome data revealed organ-specific expression of CrMTP genes and the involvement of this family in heavy metal stress responses and adaptation of C. rosea to extreme coral reef environments. Furthermore, the metal-specific activity of several functionally unknown CrMTPs was investigated in yeast. These results will contribute to uncovering the potential functions and molecular mechanisms of heavy metal absorption, translocation, and accumulation in C. rosea plants.

Highlights

Heavy metals (HMs) play essential roles as the necessary cofactors of some metabolismrelated enzymes, transcription factors, and signal transduction pathways at low levels
Bioinformatics analysis showed that all CrMTPs contained the Cation_efflux domain (PF01545), thereby suggesting that these possess a basic characteristic of the metal tolerance proteins (MTPs) family
Members of the CrMTP gene family were subdivided into classes Zn-cation diffusion facilitators (CDFs), Mn-CDF, and Zn/Fe-CDF according to their homologies with AtMTPs (Figure 1)

Summary

Introduction

Heavy metals (HMs) play essential roles as the necessary cofactors of some metabolismrelated enzymes, transcription factors, and signal transduction pathways at low levels. When they are present at high concentrations, these HMs can cause harmful effects on plant growth and cellular metabolism. Other nonessential HMs, such as cadmium (Cd), mercury (Hg), silver (Ag), and lead (Pb), even at an extremely low level, are highly toxic to plants [1]. The toxic effects of nonessential HMs or excess essential HMs to plants include causing oxidative damage and metabolic disorders, resulting in chlorosis, necrosis, and growth inhibition [3]

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Results

Discussion

Conclusion