Functional screening of cDNA library from a salt tolerant rice genotype Pokkali identifies mannose-1-phosphate guanyl transferase gene (OsMPG1) as a key member of salinity stress response

Abstract

Salinity, one of the most deleterious stresses, affects growth and overall yield of crop plants. To identify new "candidate genes" having potential role in salinity tolerance, we have carried out 'functional screening' of a cDNA library (made from a salt tolerant rice-Pokkali). Based on this screening, we identified a cDNA clone that was allowing yeast cells to grow in the presence of 1.2 M NaCl. Sequencing and BLAST search identified it as mannose-1-phosphate guanyl transferase (OsMPG1) gene from rice. Analysis of rice genome sequence database indicated the presence of 3 additional genes for MPG. Out of four, three MPG genes viz. OsMPG1, 3 and 4 were able to functionally complement yeast MPG mutant -YDL055C. We have carried out detailed transcript profiling of all members of MPG family by qRT-PCR using two contrasting rice genotypes (IR64 and Pokkali) under different abiotic stresses (salinity, drought, oxidative stress, heat stress, cold or UV light). These MPG genes showed differential expression under various abiotic stresses with two genes (OsMPG1 and 3) showing high induction in response to multiple stresses. Analysis of rice microarray data indicated higher expression levels for OsMPG1 in specific tissues such as roots, leaves, shoot apical meristem and different stages of panicle and seed development, thereby indicating its developmental regulation. Functional validation of OsMPG1 carried out by overexpression in the transgenic tobacco revealed its involvement in enhancing salinity stress tolerance.

Knocking Down the Expression of GMPase Gene OsVTC1-1 Decreases Salt Tolerance of Rice at Seedling and Reproductive Stages

“…The qPCR results showed that, similar to the results reported by Kumar [29], the expression OsVTC1-1 is induced through salt (NaCl) treatment (Fig 1). In addition, the expression of OsVTC1-1 was also induced after oxidative stress treatment (Methyl Viologen, MV) and osmotic stress treatment (PEG 6000), although gene expression patterns showed some difference under these treatments (Fig 1).…”

“…Reproductive stage is a key period for growth and yield of rice under salt stress [45, 46]. Several studies have shown that GMPase has an important effect on tolerance of plants to salinity stress at vegetative stage, but the role of GMPase in tolerance of plants to salt stress at reproductive stage remains unclear [9, 19, 29]. Results of present study showed that GMPase OsVTC1-1 plays a critical role in salt tolerance of rice at both seedling and reproductive stages through regulating AsA biosynthesis.…”

“…Previous studies have demonstrated that GMPase is involved in response to salt stress at seedling stage [8, 9, 19, 29, 33]. A point mutation of Arabidopsis GMPase VTC1 dramatically reduces tolerance to salt stress [19].…”

“…OsVTC1-1 and OsVTC1-3 are involved in AsA biosynthesis of rice, and OsVTC1-1 is responsible for most production of AsA in rice leaf [28]. In addition, results from Kumar [29] showed that heterologous overexpression of OsVTC1-1 improved the tolerance of yeast and tobacco to salt stress, indicating that OsVTC1-1 may play an important role in the response of rice to salt stress, but the native role of GMPases in response of rice to salt stress is not well understood. To further study the function of OsVTC1-1 in the response to salt stress in rice, we knocked down the expression of OsVTC1-1 in rice by RNA interference.…”

Systematic mining of salt-tolerant genes in halophyte-Zoysia matrella through cDNA expression library screening

“…Thirty-two full length salt-tolerant genes from Jatropha curcas were identified by heterologous expression in yeast (Eswaran et al, 2010). OsMPG1 and OsKAT1 screened from rice yeast cDNA library were further confirmed as salt-tolerance genes (Kumar et al, 2012a;Obata et al, 2007). SsTypA1 and SsOEP8 identified from Suaeda salsa via yeast selection performed oxidative stress tolerance of their transgenic tobacco plants .…”