Identification of Ginger(Zingiber officinale Roscoe)NHX Gene Family Members and Characterization of Their Expression Patterns in Silicon Alleviating Salt Stress
[Objective]Systematic analysis of the basic features of the ZoNHX family members in ginger and exploration of their expression patterns in different tissues and treatments of ginger can provide a theoretical foundation for further research on the function of ZoNHXs.[Method]The Arabidopsis thaliana NHX protein sequences were used as reference sequences to compare with the ginger genome to obtain the ginger ZoNHXs.The phylogenetic tree containing Arabidopsis and ginger NHX family members were constructed based on the neighbor-joining method by MEGA 7.0.Physicochemical properties,gene structure,conserved motifs,secondary structure and tertiary structure of ZoNHXs were analyzed by using ExPASy ProtParam software,GSDS,MEME online website,PHYRE 2 and SOPMA,while chromosomal localization,intragenomic covariance and expression patterns of ZoNHXs were analyzed by using TBtools software.The gene expression levels of ZoNHXs in different treatments including CK,NaCl,and NaCl+SiNP100,and different ginger tissues were analyzed using RT-qPCR.The Na+and K+contents of ginger tissues was determined.[Result]A total of 15 NHX gene family members were identified from the ginger genome,and were named as ZoNHX 1-ZoNHX 15 based on their chromosomal locations.The ZoNHXs were classified into three subgroups according to phylogenetic relationship and subcellular localization,including vesicular membranes(Vac,vacuole),endosomal membranes in the nucleus(Endo,endosome)and plasma membranes(PM,plasma).Protein characterization analysis showed that the relative molecular weights of ZoNHXs ranged from 26.01 kDa to 163.59 kDa,and the protein lengths ranged from 231 to 1 459 aa.The results of subcellular localization prediction showed that 11 ZoNHXs were distributed on the vacuole,ZoNHX14 were distributed both on the cell membrane and nucleus,ZoNHX1,ZoNHX7 and ZoNHX9 were respectively distributed on cytoplasm,cell membrane,and chloroplast.Signal peptide prediction showed that only ZoNHX1 contained a signal peptide and was a secreted protein,while other ZoNHX family members were non-secretory proteins.Cis-acting element analysis showed that the promoter regions of the ZoNHXs contain growth and development response elements,hormone response elements,and stress response elements.Transcriptome analysis showed that all ZoNHXs were detected to be expressed in ginger leaf and root,among which,ZoNHX12 was highly expressed in all tissues of ginger and under different abiotic stresses,and ZoNHX14 was significantly up-regulated in all growth periods of ginger and at low temperatures.RT-qPCR results showed that,compared with the CK,all genes were significantly up-regulated in roots and leaves after salt stress except for ZoNHX8 and ZoNHX11.Compared with the NaCl treatment alone,NaCl+SiNP100 decreased the expression levels of all genes except for ZoNHX8 and ZoNHX11,the expression levels of which were significantly up-regulated.These indicated that ZoNHXs were involved in the response process of ginger to salt stress and the expression of ZoNHXs were also regulated by exogenous SiNP100.The results of Na+,K+ion content,K+/Na+ratio and transport selection coefficient SK+/Na+showed that the Na+content in ginger rhizomes,stems,and leaves under salt treatment was increased compared with CK,and the K+/Na+ratio and transport selection coefficient were decreased.NaCl+SiNP100 treatment significantly decreased Na+content in roots,rhizomes,stems and leaves,whereases increased K+/Na+ratio and transport selection coefficient.[Conclusion]The ginger genome contains 15 ZoNHXs and divides into three subgroups.RT-qPCR results showed that the expression of ZoNHX1-ZoNHX15 were all induced by salt stress.SiNPl00 pretreatment could alleviate plant salt stress through reducing the Na+content and increase the K+/Na+ratio and K+and Na+content of the ginger roots,rhizomes,stems,and leaves by regulating the expression of ZoNHXs.
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