Improvement of water use efficiency in rice by expression of HARDY , an Arabidopsis drought and salt tolerance gene

Abstract

Freshwater is a limited and dwindling global resource; therefore, efficient water use is required for food crops that have high water demands, such as rice, or for the production of sustainable energy biomass. We show here that expression of the Arabidopsis HARDY (HRD) gene in rice improves water use efficiency, the ratio of biomass produced to the water used, by enhancing photosynthetic assimilation and reducing transpiration. These drought-tolerant, low-water-consuming rice plants exhibit increased shoot biomass under well irrigated conditions and an adaptive increase in root biomass under drought stress. The HRD gene, an AP2/ERF-like transcription factor, identified by a gain-of-function Arabidopsis mutant hrd-D having roots with enhanced strength, branching, and cortical cells, exhibits drought resistance and salt tolerance, accompanied by an enhancement in the expression of abiotic stress associated genes. HRD overexpression in Arabidopsis produces thicker leaves with more chloroplast-bearing mesophyll cells, and in rice, there is an increase in leaf biomass and bundle sheath cells that probably contributes to the enhanced photosynthesis assimilation and efficiency. The results exemplify application of a gene identified from the model plant Arabidopsis for the improvement of water use efficiency coincident with drought resistance in the crop plant rice.biomass ͉ bundle sheath ͉ photosynthesis ͉ root strength ͉ transcription factor

The Potential of Transcription Factor-Based Genetic Engineering in Improving Crop Tolerance to Drought

“…Many genetically engineered plants have shown phenotypes with improved tolerance under water-limited conditions (Umezawa et al, 2006;Vinocur and Altman, 2005). Most of these published results were based on the analysis of transgenic model plants such as Arabidopsis and were further extended to some major crop species such as rice (Karaba et al, 2007), soybean (Seo et al, 2012), and maize (Zhang et al, 2004). Because of the complexity of the trait involved, understanding the genetic basis of drought tolerance is a necessary step in many strategies to develop a drought-tolerant crop.…”

Emerging tools, concepts and ideas to track the modulator genes underlying plant drought adaptive traits: An overview

“…64 A number of genes have been identified to be involved in CT, and their functions were confirmed by transgenic approaches. 2,7,11,[65][66][67] It has also been reported recently that ectopic expression of stress specific transcription factors in combination aids in combating multiple abiotic stresses. [68][69][70] Large numbers of review articles have compiled the relevance of multiple upstream regulatory as well as downstream functional genes underlying a wide array of drought tolerance traits in imparting abiotic stress tolerance ( Table 2).…”

“…10 Improvement in root branching and density can lead to drought tolerance as noticed in rice using transgenic approach. 11 Many other root attributes have been reviewed extensively in the recent past. [12][13] There are also recent evidences emphasizing the importance of combining water acquisition and CT traits for maintaining higher spikelet fertility in rice under drought stress thereby enhancing field level tolerance to water limitation.…”

Identification and freedom to operate analysis of potential genes for drought tolerance in maize

“…The most commonly used TFs in transgenic-induced drought tolerance are DREB/ CBF and zinc-finger proteins (ZFP252, WRKI, ZPT2-3, SAP, STZ, AZF2 , ZAT10 and others). Other TFs or transcription activators such as AP37 (Oh et al, 2009), AREB1 (Kang et al, 2002;Fujita et al, 2005), NAC (Hu et al, 2006), HARDY (Karaba et al, 2007), MYB (Ding et al, 2009), and NF-Y (Nelson et al, 2007;Li et al, 2008) have been used to increase drought tolerance through genetic engineering.…”