RESUMEN
Development of high yield rice varieties is critical to ensuring global food security. However, the emission of greenhouse gases (GHG) such as Methane (CH4) and Nitrous oxide (N2O) from paddy fields threatens environmental sustainability. In this study, we selected overexpressed high-affinity nitrate transporters (NRT2.3 along with their partner protein NAR2.1) cultivars, which are effective nitrogen use efficient transgenic lines pOsNAR2.1: OsNAR2.1 (Ox2) and p35S:OsNRT2.3b (O8). We used high (270 kg N/ha) and low (90 kg N/ha) nitrogen (N) fertilizers in paddy fields to evaluate morphophysiological traits, including GHG emission. We found that Ox2 and O8 reduced CH4 emissions by 40% and 60%, respectively, compared to their wild type (WT). During growth stages, there was no consistent N2O discharge pattern between WT and transgenics (Ox2, O8) in low and high N application. However, total cumulative N2O in a cropping season reduced in O8 and increased in Ox2 cultivars, compared to WT. Root aerenchyma formation reduced by 30-60% in transgenic lines. Methanogens like mcrA in low and high N were also reduced by up to 50% from rhizosphere of Ox2 and O8. However, the nitrifying bacterial population such as nosZ reduced in both transgenics significantly, but nirK and nirS did not show a consistent variation. The high yield of transgenic rice with limited aerenchyma mitigates the discharge of CH4 and N2O by reducing root exudates that provide substrates for GHG. Our results improve understanding for breeders to serve the purpose of sustainable development.
RESUMEN
The OsNRT2.3a and OsNRT2.3b isoforms play important roles in the uptake and transport of nitrate during rice growth. However, it is unclear which cis-acting element controls the transcription of OsNRT2.3 into these specific isoforms. In this study, we used a yeast one-hybrid assay to obtain the TATA-box binding protein OsTBP2.1, which binds to the TATA-box of OsNRT2.3, and verified its important role through transient expression and RNA-seq. We found that the TATA-box of OsNRT2.3 mutants and binding protein OsTBP2.1 together increased the transcription ratio of OsNRT2.3b to OsNRT2.3a. The overexpression of OsTBP2.1 promoted nitrogen uptake and increased rice yield compared with the wild-type; however, the OsTBP2.1 T-DNA mutant lines exhibited the opposite trend. Detailed analyses demonstrated that the TATA-box was the key cis-regulatory element for OsNRT2.3 to be transcribed into OsNRT2.3a and OsNRT2.3b. Additionally, this key cis-regulatory element, together with the binding protein OsTBP2.1, promoted the development of rice and increased grain yield.
Asunto(s)
Oryza , Proteínas de Transporte de Anión/metabolismo , Grano Comestible/genética , Regulación de la Expresión Génica de las Plantas , Transportadores de Nitrato , Nitratos/metabolismo , Nitrógeno/metabolismo , Oryza/metabolismo , Proteínas de Plantas/genética , Proteínas de Plantas/metabolismo , Raíces de Plantas/metabolismo , TATA Box , Proteína de Unión a TATA-Box/genética , Proteína de Unión a TATA-Box/metabolismoRESUMEN
Greenhouse gasses (GHG) emission from the agricultural lands is a serious threat to the environment. Plants such as rice (Oryza sativa L.) that are cultivated in submerged conditions (paddy field) contribute up to 19% of CH4 emission from agricultural lands. Such plants have evolved lysigenous aerenchyma in their root system which facilitates the exchange of O2 and GHG between aerial parts of plant and rhizosphere. Currently, the regulation of GHG and O2 via aerenchyma formation is poorly understood in plants, especially in rice. Here, a reverse genetic approach was employed to reduce the aerenchyma formation by analyzing two mutants i.e., oslsd1.1-m12 and oslsd1.1-m51 generated by Tos17 and T-DNA insertion. The wild-type (WT) and the mutants were grown in paddy (flooded), non-paddy and hydroponic system to assess phenotypic traits including O2 diffusion, GHG emission and aerenchyma formation. The mutants exhibited significant reductions in several morphophysiological traits including 20-60% aerenchyma formation at various distances from the root apex, 25% root development, 50% diffusion of O2 and 27-36% emission of methane (CH4) as compared to WT. The differential effects of the oslsd1.1 mutants in aerenchyma-mediated CH4 mitigation were also evident in the diversity of (pmoA, mcrA) methanotrophs in the rhizosphere. Our results indicate the novel pathway in which reduced aerenchyma in rice is responsible for the mitigation of CH4, diffusion of O2 and the root growth in rice. Limited aerenchyma mediated approach to mitigate GHG specially CH4 mitigation in agriculture is helpful technique for sustainable development.
Asunto(s)
Gases de Efecto Invernadero , Oryza , Agricultura , Metano/análisis , Oxígeno , SueloRESUMEN
Drought is an important environmental factor that severely restricts crop production. The high-affinity nitrate transporter partner protein OsNAR2.1 plays an essential role in nitrate absorption and translocation in rice. Our results suggest that OsNAR2.1 expression is markedly induced by water deficit. After drought stress conditions and irrigation, compared with wild-type (WT), the survival rate was significantly improved in OsNAR2.1 over-expression lines and decreased in OsNAR2.1 RNAi lines. The survival rate of Wuyunjing7 (WYJ), OsNRT2.1 over-expression lines and OsNRT2.3a over-expression lines was not significantly different. Compared with WT, overexpression of OsNAR2.1 could significantly increase nitrogen uptake in rice, and OsNAR2.1 RNAi could significantly reduce nitrogen uptake. Under drought conditions, the expression of OsNAC10, OsSNAC1, OsDREB2a, and OsAP37 was significantly reduced in OsNAR2.1 RNAi lines and increased substantially in OsNAR2.1 over-expression lines. Also, the chlorophyll content, relative water content, photosynthetic rate and water use efficiency were decreased considerably in OsNAR2.1 RNAi lines and increased significantly in OsNAR2.1 over-expression lines under drought conditions. Finally, compared to WT, grain yield increased by about 9.1 and 26.6%, in OsNAR2.1 over-expression lines under full and limited irrigation conditions, respectively. These results indicate that OsNAR2.1 regulates the response to drought stress in rice and increases drought tolerance.