Overexpression of the Transcription FactorAP37in Rice Improves Grain Yield under Drought Conditions    

Abstract

Transcription factors with an APETELA2 (AP2) domain have been implicated in various cellular processes involved in plant development and stress responses. Of the 139 AP2 genes predicted in rice (Oryza sativa), we identified 42 genes in our current study that are induced by one or more stress conditions, including drought, high salinity, low temperature, and abscisic acid. Phylogenic analysis of these 42 stress-inducible AP2 genes revealed the presence of six subgroups (I-VI) with distinct signature motifs. Two genes, AP37 and AP59, representing subgroups I and II, respectively, were functionally characterized. Both genes were found to be induced upon 2 h of exposure to drought and high-salinity conditions but to differ in their expression profile upon exposure to low temperature and abscisic acid. The overexpression of AP37 and AP59 in rice under the control of the constitutive promoter OsCc1 increased the tolerance to drought and high salinity at the vegetative stage. Increased tolerance to low temperatures was observed only in OsCc1:AP37 plants. More importantly, the OsCc1:AP37 plants showed significantly enhanced drought tolerance in the field, which increased grain yield by 16% to 57% over controls under severe drought conditions, yet exhibited no significant difference under normal growth conditions. In contrast, grain yield in OsCc1:AP59 plants in the field was reduced by 23% to 43% compared with controls under both normal and drought stress conditions. Microarray experiments identified 10 and 38 genes that are up-regulated by AP37 and AP59, respectively, in addition to 37 genes that are commonly induced by both factors. Our results suggest that the AP37 gene has the potential to improve drought tolerance in rice without causing undesirable growth phenotypes.

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 .…”

SALT-RESPONSIVE ERF1 Regulates Reactive Oxygen Species-Dependent Signaling during the Initial Response to Salt Stress in Rice

“…DREB2A and AP37 represent positive regulators of salt tolerance (Oh et al, 2009;Mallikarjuna et al, 2011), both of which were induced in stressed wild-type roots ( Figure 4B). By contrast, DREB2A was not responsive, and AP37 showed an attenuated response in serf1 and SERF1 knockdown lines upon salt stress ( Figure 4B; see Supplemental Table 4 online).…”

Physiological, Morphological and Molecular Mechanisms for Drought Tolerance in Rice

“…Stress-responsive rice SNAC genes such as SNAC1, OsNAC6/SNAC2 and OsNAC5 improve drought tolerance when overexpressed (Hu et al, 2006;Takahashi et al, 2010;Nakashima et al, 2014). Many TFs have been used to produce transgenic rice lines with either constitutive or inducible promoters, such as HvCBF4, AP37 Oh et al, 2009), TaSTRG, OsDREB1A, OsDREB1B (Datta et al, 2012), AtDREB1A (Hussain et al, 2014;Ravikumar et al, 2014), OsNAC6 (Rachmat et al, 2014) (Fig. 1).…”