Abstract
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.
Highlights
Salinity is one of the major environment factors that limits crops productivity worldwide [1]
The results showed that a total of five full-length genes coding putative Na+ /H+ antiporter (NHX) was identified in the sugar beet genome and the sequences were downloaded from the sugar beet genome database (Supplementary Table Solanum lycopersicum (Sl))
Phylogenetic analysis revealed that these NHX genes are grouped into three major classes, viz Vac-(BvNHX1, -2 and
Summary
Salinity is one of the major environment factors that limits crops productivity worldwide [1]. It is estimated that approximately 20% of cultivated land and one half of irrigated land worldwide suffers salinity damage [2]. Salt stress has a vital effect on the growth and development of plants [3]. High saline soils reduce the ability to uptake water and nutrients, resulting in osmotic or water-deficit stress [4]. To cope with salt stress, plants have evolved a series of smart and precise mechanisms, including regulation of growth and development, ion homeostasis, detoxification, and osmotic adjustment [5]. The maintenance of ion homeostasis is one of the most important strategies for plants adaptive to salt stress [6]
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