Chang Yu, Nguyen Ba Hoanh, Xie Yongjun, Xiao Benze, Tang Ning, Zhu Wenliu, Mou Tongmin, Xiong Lizhong
National Key Laboratory of Crop Genetic Improvement, Huazhong Agricultural UniversityWuhan, China.
Institute of Natural Sciences Education, Vinh UniversityVinh, Vietnam.
Front Plant Sci. 2017 Jun 26;8:1102. doi: 10.3389/fpls.2017.01102. eCollection 2017.
Drought is one of the major abiotic stresses threatening rice () production worldwide. Drought resistance is controlled by multiple genes, and therefore, a multi-gene genetic engineering strategy is theoretically useful for improving drought resistance. However, the experimental evidence for such a strategy is still lacking. In this study, a few drought-responsive genes from rice were assembled by a multiple-round site-specific assembly system, and the constructs were introduced into the rice cultivar KY131 via -mediated transformation. The transgenic lines of the multi-gene and corresponding single-gene constructs were pre-evaluated for drought resistance. We found that the co-overexpression of two genes, encoding a constitutively active form of a bZIP transcription factor () and a protein kinase () involved in the abscisic acid signaling pathway, showed significantly enhanced drought resistance compared with the single-gene transgenic lines and the negative transgenic plants. Single-copy lines of this bi-gene combination (named XL22) and the corresponding single-gene lines were further evaluated for drought resistance in the field using agronomical traits. The results showed that XL22 exhibited greater yield, biomass, spikelet number, and grain number under moderate drought stress conditions. The seedling survival rate of XL22 and the single-gene overexpressors after drought stress treatment also supported the drought resistance results. Furthermore, expression profiling by RNA-Seq revealed that many genes involved in the stress response were specifically up-regulated in the drought-treated XL22 lines and some of the stress-related genes activated in CA1-OE and SAPK6-OE were distinct, which could partially explain the different performances of these lines with respect to drought resistance. In addition, the XL22 seedlings showed improved tolerance to heat and cold stresses. Our results demonstrate that the multi-gene assembly in an appropriate combination may be a promising approach in the genetic improvement of drought resistance.
干旱是威胁全球水稻生产的主要非生物胁迫之一。抗旱性由多个基因控制，因此，多基因遗传工程策略理论上有助于提高抗旱性。然而，仍缺乏该策略的实验证据。在本研究中，通过多轮位点特异性组装系统组装了一些来自水稻的干旱响应基因，并通过农杆菌介导的转化将构建体导入水稻品种KY131。对多基因构建体和相应单基因构建体的转基因株系进行了抗旱性预评估。我们发现，与单基因转基因株系和阴性转基因植株相比，编码组成型活性形式的bZIP转录因子（CA1）和参与脱落酸信号通路的蛋白激酶（SAPK6）的两个基因的共过表达显著增强了抗旱性。对该双基因组合（命名为XL22）的单拷贝株系和相应的单基因株系在田间利用农艺性状进一步评估了抗旱性。结果表明，在中度干旱胁迫条件下，XL22表现出更高的产量、生物量、小穗数和粒数。干旱胁迫处理后XL22和单基因过表达株系的幼苗存活率也支持了抗旱性结果。此外，通过RNA-Seq进行的表达谱分析表明，许多参与胁迫反应的基因在干旱处理的XL22株系中特异性上调，并且在CA1-OE和SAPK6-OE中激活的一些胁迫相关基因是不同的，这可以部分解释这些株系在抗旱性方面的不同表现。此外，XL22幼苗对热胁迫和冷胁迫的耐受性有所提高。我们的结果表明，以适当组合进行多基因组装可能是遗传改良抗旱性的一种有前景的方法。
