Root-Specific Expression ofOsNAC10Improves Drought Tolerance and Grain Yield in Rice under Field Drought Conditions    

Abstract

Drought poses a serious threat to the sustainability of rice (Oryza sativa) yields in rain-fed agriculture. Here, we report the results of a functional genomics approach that identified a rice NAC (an acronym for NAM [No Apical Meristem], ATAF1-2, and CUC2 [Cup-Shaped Cotyledon]) domain gene, OsNAC10, which improved performance of transgenic rice plants under field drought conditions. Of the 140 OsNAC genes predicted in rice, 18 were identified to be induced by stress conditions. Phylogenic analysis of the 18 OsNAC genes revealed the presence of three subgroups with distinct signature motifs. A group of OsNAC genes were prescreened for enhanced stress tolerance when overexpressed in rice. OsNAC10, one of the effective members selected from prescreening, is expressed predominantly in roots and panicles and induced by drought, high salinity, and abscisic acid. Overexpression of OsNAC10 in rice under the control of the constitutive promoter GOS2 and the root-specific promoter RCc3 increased the plant tolerance to drought, high salinity, and low temperature at the vegetative stage. More importantly, the RCc3: OsNAC10 plants showed significantly enhanced drought tolerance at the reproductive stage, increasing grain yield by 25% to 42% and by 5% to 14% over controls in the field under drought and normal conditions, respectively. Grain yield of GOS2: OsNAC10 plants in the field, in contrast, remained similar to that of controls under both normal and drought conditions. These differences in performance under field drought conditions reflect the differences in expression of OsNAC10-dependent target genes in roots as well as in leaves of the two transgenic plants, as revealed by microarray analyses. Root diameter of the RCc3: OsNAC10 plants was thicker by 1.25-fold than that of the GOS2:OsNAC10 and nontransgenic plants due to the enlarged stele, cortex, and epidermis. Overall, our results demonstrated that root-specific overexpression of OsNAC10 enlarges roots, enhancing drought tolerance of transgenic plants, which increases grain yield significantly under field drought conditions. Plants respond and adapt to abiotic stresses to survive under adverse conditions. Upon exposure of plants to such stresses, many genes are induced, and their products are involved in the protection of cellular machinery from stress-induced damage (Bray, 1993;Thomashow, 1999;Shinozaki et al., 2003). The expression of stress-related genes is largely regulated by specific transcription factors. The overexpression of such transcription factor genes often results in activation of many functional genes related to the particular stress conditions, consequently conferring stress tolerance. For example, the DREB1A/CBF3 gene in transgenic Arabidopsis (Arabidopsis thaliana) activates expression of its stress-related downstream genes, thereby enhancing stress tolerance (Liu et al., 1998;Kasuga et al., 1999).The rice (Oryza sativa) and Arabidopsis genomes each encode more than 1,300 transcriptional regulators, which account for 6% of the estimated total nu...

Posttranscriptional Control of Photosynthetic mRNA Decay under Stress Conditions Requires 3′ and 5′ Untranslated Regions and Correlates with Differential Polysome Association in Rice

“…We have previously identified stress-regulated genes in rice plants through expression profiling using the Rice 39-Tiling microarray (GreenGene Biotech) and RNAs from the 14-d-old leaves of rice seedlings subjected to drought, high salt, and low temperature (Oh et al, 2009;Jeong et al, 2010). In addition to up-regulated genes, we also identified many genes that were down-regulated under stress conditions, including most of the photosynthetic genes involved in light and dark reactions.…”

“…Each plant was grown in a pot (4 3 4 3 5 cm 3 ; six plants per pot) filled with rice nursery soil (Bio-Media) for 14 d after germination. Stress treatments were performed as described previously (Oh et al, 2009;Jeong et al, 2010;Redillas et al, 2011). Briefly, for drought stress, 14-d seedlings were air dried in the greenhouse under continuous light of approximately 900 to 1,000 mmol m 22 s 21 .…”

Drought-tolerance QTLs commonly detected in two sets of reciprocal introgression lines in rice

“…QTL QSnp3a controlling SpNP detected in the two sets of ILs, and QSf3, QFgwp3 and QGyp3 for SF, FGWP and GYP detected in the TQ-ILs were mapped together with OsTIFY11a in the region of 3502670-4681740 on chromosome 3, which encodes a ZIM family gene exhibiting significant improvement in tolerance against drought and high salinity when overexpressed in transgenic rice plants (Ye et al 2009). QTL QSnp11 affecting SpNP detected in the two sets of ILs, and QFgwp11a and QGyp11 underlying FGWP and GYP detected in the TQ-ILs, were mapped together with two NAC TF genes in the region of 749467-1767997 on chromosome 11, OsNAC10, which was associated with significantly increased DT (Jeong et al 2010), and OsNAC045, which could be induced by drought, high salinity and abscisic acid (Xiao et al 2007;Zheng et al 2009). QTL QPh9 governing PH, which was localised in 17141056-18060875 on chromosome 9 in TQ-ILs, was mapped together with OsbZIP72 encoding a zinc-finger TF, which was a positive regulator of ABA response and DT in rice ).…”

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

“…NAC TFs have been reported during drought in rice (Rabbani et al, 2003;Zhou et al, 2007) and Arabidopsis (Matsui et al, 2008;Tran et al, 2010). The use of NAC TFs as tools to improve drought tolerance in rice (Hu et al, 2006;Jeong et al, 2010;Zheng et al, 2009), tobacco (Ramegowda et al, 2012), wheat (Xue et al, 2011), and Arabidopsis (Gao et al, 2010) has also been reported.…”

“…Overexpression of another rice SNAC gene, SNAC2, showed tolerance to polyethylene glycol (PEG), cold, and salinity treatments in the rice seedlings (Hu et al, 2008). In a separate field trial, there was a 42% increase in grain yield in OsNAC10-overexpressing transgenic rice under drought conditions ( Jeong et al, 2010). Heterologous expression of rice SNAC1 in transgenic wheat resulted in improved drought tolerance of transgenic rice under controlled growth conditions (Saad, 2013).…”