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Abstract
Salinity-affected and heavy metal-contaminated soils limit the growth of glycophytic plants. Identifying genes responsible for superior tolerance to salinity and heavy metals in halophytes has great potential for use in developing salinity- and Cd-tolerant glycophytes. The objective of this study was to identify salinity- and Cd-tolerance related genes in seashore paspalum (Paspalum vaginatum), a halophytic perennial grass species, using yeast cDNA expression library screening method. Based on the Gateway-compatible vector system, a high-quality entry library was constructed, which contained 9.9 × 106 clones with an average inserted fragment length of 1.48 kb representing a 100% full-length rate. The yeast expression libraries were screened in a salinity-sensitive and a Cd-sensitive yeast mutant. The screening yielded 32 salinity-tolerant clones harboring 18 salinity-tolerance genes and 20 Cd-tolerant clones, including five Cd-tolerance genes. qPCR analysis confirmed that most of the 18 salinity-tolerance and five Cd-tolerance genes were up-regulated at the transcript level in response to salinity or Cd stress in seashore paspalum. Functional analysis indicated that salinity-tolerance genes from seashore paspalum could be involved mainly in photosynthetic metabolism, antioxidant systems, protein modification, iron transport, vesicle traffic, and phospholipid biosynthesis. Cd-tolerance genes could be associated with regulating pathways that are involved in phytochelatin synthesis, HSFA4-related stress protection, CYP450 complex, and sugar metabolism. The 18 salinity-tolerance genes and five Cd-tolerance genes could be potentially used as candidate genes for genetic modification of glycophytic grass species to improve salinity and Cd tolerance and for further analysis of molecular mechanisms regulating salinity and Cd tolerance.
Highlights
Fresh water availability for agricultural and horticultural irrigation has decreased, whereas there has been an increased use of recycled and effluent water for irrigation, which contains a high content of salinity and heavy metals that leads to soil salinization and heavy metal contamination (Uddin et al, 2011; Azevedo et al, 2012; Pessarakli, 2014)
Our results indicated that a 14-3-3 family member and a LRR-RKs member of seashore paspalum could positively regulate salinity tolerance, which is in disagreement with what was previously found in Arabidopsis or rice
This study identified 18 salinity-tolerance and five Cdtolerance genes in seashore paspalum through full-length cDNA library screening in yeast and confirmation of gene expression in seashore paspalum exposed to salinity or Cd treatment using qPCR analysis
Summary
Fresh water availability for agricultural and horticultural irrigation has decreased, whereas there has been an increased use of recycled and effluent water for irrigation, which contains a high content of salinity and heavy metals that leads to soil salinization and heavy metal contamination (Uddin et al, 2011; Azevedo et al, 2012; Pessarakli, 2014). Functional characterization of genes conferring plant tolerance to salinity or Cd will help to further understand the molecular mechanisms controlling abiotic stress tolerance. Yeast has been utilized for functional assays or screening of plant stress-tolerance genes due to the simplicity as single cells, rapid growth, and the availability of mutants sensitive to various abiotic stresses (Qiu, 2012). Several Cd-tolerance related genes, including aquaporin and protease inhibitors and metallothionein, were identified from rice (Oryza sativa) with FOX-gene hunting system, as those genes could restore Cd tolerance in Cd-sensitive yeast mutants (Wang et al, 2012). For halophytic plant species that adapt to chronically severe salinity conditions, are yet to be completely understood and deserve further exploration
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