Enhanced Salt Tolerance Conferred by the Complete 2.3 kb cDNA of the Rice Vacuolar Na+/H+ Antiporter Gene Compared to 1.9 kb Coding Region with 5′ UTR in Transgenic Lines of Rice

Abstract

Soil salinity is one of the most challenging problems that restricts the normal growth and production of rice worldwide. It has therefore become very important to produce more saline tolerant rice varieties. This study shows constitutive over-expression of the vacuolar Na+/H+ antiporter gene (OsNHX1) from the rice landrace (Pokkali) and attainment of enhanced level of salinity tolerance in transgenic rice plants. It also shows that inclusion of the complete un-translated regions (UTRs) of the alternatively spliced OsNHX1 gene provides a higher level of tolerance to the transgenic rice. Two separate transformation events of the OsNHX1 gene, one with 1.9 kb region containing the 5′ UTR with CDS and the other of 2.3 kb, including 5′ UTR, CDS, and the 3′ UTR regions were performed. The transgenic plants with these two different constructs were advanced to the T3 generation and physiological and molecular screening of homozygous plants was conducted at seedling and reproductive stages under salinity (NaCl) stress. Both transgenic lines were observed to be tolerant compared to WT plants at both physiological stages. However, the transgenic lines containing the CDS with both the 5′ and 3′ UTR were significantly more tolerant compared to the transgenic lines containing OsNHX1 gene without the 3′ UTR. At the seedling stage at 12 dS/m stress, the chlorophyll content was significantly higher (P < 0.05) and the electrolyte leakage significantly lower (P < 0.05) in the order 2.3 kb > 1.9 kb > and WT lines. Yield in g/plant in the best line from the 2.3 kb plants was significantly more (P < 0.01) compared, respectively, to the best 1.9 kb line and WT plants at stress of 6 dS/m. Transformation with the complete transcripts rather than the CDS may therefore provide more durable level of tolerance.

Downregulation of the DST Transcription Factor Using Artificial microRNA to Increase Yield, Salt and Drought Tolerance in Rice

“…Most of the studies involving the ectopic insertion of transgenes show some reduction in yield in abiotic stress conditions [10]. Previous studies on DST separately showed abiotic stress tolerance and enhanced yield in rice [16] [20].…”

“…The disks were floated in a 20 ml solution of 150 mM NaCl for T 0 transgenic lines for 4 days at 25˚C. The analysis was carried out with three biological replicates in three independent experiments [10].…”

“…As a result, engineering of multiple genes or regulatory genes (such as gene for transcription regulators, like SNAC1, HARDY) instead of a single stress related gene can augment better tolerance to environmental stresses [8] [9]. Nevertheless, stress tolerant transgenic lines generally show some loss in grain yield production under stress [10]. So, development of rice which is simultaneously high yielding as well as stress tolerant is crucial to ensure food security.…”

Natural variation in growth and physiology under salt stress in rice: QTL mapping in aHorkuch×IR29mapping population at seedling and reproductive stages

“…It has been reported that Pokkali maintain lower shoot Na + accumulation and lower shoot Na + /K + ratio under high salinity compared to sensitive genotypes (Kavitha et al , 2012; Sexcion et al , 2009). The enhancement of salinity tolerance by constitutive overexpression of the vacuolar Na + /H + antiporter gene from Pokkali in transgenic rice plants suggest that this landrace may use a tissue tolerance mechanism to lower shoot Na + /K + ratio under high salinity (Amin et al , 2016). Negrao et al genotyped 392 rice accessions by EcoTILLING in order to understand allelic difference for salt stress.…”

Relative Response of Indigenous Rice Genotypes to Low Versus Normal Planting Density for Determination of Differential Phenotypic Plasticity in Traits Related to Grain Yield

“…Use of plant dwarfism as ideal plant architecture as exemplified in the green revolution, has already reached its biological limit and has little room for improvement (Zhu et al 2010, Srinivasan et al 2017. Moreover, climate change also poses both abiotic and biotic threats, like drought, heat, salinity, sea level rise, new predatory insects, pesticide resistant pests as well as elevated level of greenhouse gases like CO 2 (Kant et al 2012, Amin et al 2016. The drastic change in the level of atmospheric CO 2 ([CO 2 ]), primarily caused by the industrial revolution which is predicted to increase by almost 50% by mid-century due to anthropogenic changes (Shimono et al 2014, Bishop et al 2015.…”