Salinity is one of the major environment factors that limits the growth of plants and the productivity of crops worldwide. It has been shown that Na⁺ transporters play a central role in salt tolerance and development of plants. The objective of this study was to identify Na⁺/H⁺ antiporter (NHX) genes and investigate their expression patterns in sugar beet (Beta vulgaris L.) subjected to various concentrations of NaCl. A total of five putative NHX genes were identified and distributed on four chromosomes in sugar beet. Phylogenetic analysis revealed that these BvNHX genes are grouped into three major classes, viz Vac- (BvNHX1, -2 and -3), Endo- (BvNHX4), and PM-class NHX (BvNHX5/BvSOS1), and within each class the exon/intron structures are conserved. The amiloride-binding site is found in TM3 at N-terminus of Vac-class NHX proteins. Protein-protein interaction (PPI) prediction suggested that only BvNHX5 putatively interacts with calcineurin B-like proteins (CBL) and CBL-interacting protein kinases (CIPK), implying it might be the primary NHX involved in CBL-CIPK pathway under saline condition. It was also found that BvNHX5 contains one abscisic acid (ABA)-responsive element (ABRE), suggesting that BvNHX5 might be involved in ABA signal responsiveness. Additionally, the qRT-PCR analysis showed that all the BvNHX genes in both roots and leaves are significantly up-regulated by salt, and the transcription levels under high salinity are significantly higher than those under either low or moderate salinity. Taken together, this work gives a detailed overview of the BvNHX genes and their expression patterns under salt stress. Our findings also provide useful information for elucidating the molecular mechanisms of Na⁺ homeostasis and further functional identification of the BvNHX genes in sugar beet.

Open Access Agricultural Journals published by Institute of Agricultural Economics and Information

Background: The WRKY transcription factor family plays crucial roles in many aspects of physiological processes and adaption to environment. Although theWRKYgenes have been widely identified in various plant species, the structure and function of theWRKYfamily in sugar beet (Beta vulgarisL.) remains unknown.Methods: In the present study, theWRKYgenes were identified from the sugar beet genome by bioinformatics. A phylogenetic tree was constructed by MEGA7.0. A distribution map of these genes was displayed by MapInspect 1.0. Furthermore, the exon-intron structure and the conserved motifs were predicted by GSDS 2.0 and MEME 5.0.5, respectively. Additionally, the expression levels of nine selected genes in shoots and roots of sugar beet seedlings exposed to alkaline stress were assayed by qRT-PCR.Results: A total of 58 putativeBvWRKYgenes are identified in the sugar beet genome. The coding sequences of these genes ranged from 558 to 2,307 bp and molecular weights (MWs) varied from 21.3 to 84. TheBvWRKYgenes are clustered into three major groups I, II, and III, with 11, 40, and seven members, based on the primary amino acid sequences. The number of introns in theBvWRKYgenes ranged from 1 to 5, with a majority ofBvWRKY(27/58) containing three exons. All theBvWRKYgenes have one or two conserved WRKY domains and zinc-finger structure. Moreover, the selectedBvWRKYgenes showed a variety of expression patterns in shoots and roots of seedlings under various concentrations of NaHCO₃. Importantly,BvWRKY10in shoots andBvWRKY16in roots were remarkably up-regulated by alkaline stress. Taken together, our findings extend understandings of theBvWRKYgenes family and provide useful information for subsequent research on their functions in sugar beet under alkaline stress.