Li Zhao, Hu Guanghui, Liu Xiangfeng, Zhou Yao, Li Yu, Zhang Xu, Yuan Xiaohui, Zhang Qian, Yang Deguang, Wang Tianyu, Zhang Zhiwu
Agronomy College of Northeast Agricultural UniversityHarbin, China; Department of Crop and Soil Sciences, Washington State UniversityPullman, WA, USA.
Agronomy College of Northeast Agricultural UniversityHarbin, China; Department of Crop and Soil Sciences, Washington State UniversityPullman, WA, USA; Institute of Maize Research, Heilongjiang Academy of Agricultural SciencesHarbin, China.
Front Plant Sci. 2016 Oct 7;7:1477. doi: 10.3389/fpls.2016.01477. eCollection 2016.
Originating in a tropical climate, maize has faced great challenges as cultivation has expanded to the majority of the world's temperate zones. In these zones, frost and cold temperatures are major factors that prevent maize from reaching its full yield potential. Among 30 elite maize inbred lines adapted to northern China, we identified two lines of extreme, but opposite, freezing tolerance levels-highly tolerant and highly sensitive. During the seedling stage of these two lines, we used RNA-seq to measure changes in maize whole genome transcriptome before and after freezing treatment. In total, 19,794 genes were expressed, of which 4550 exhibited differential expression due to either treatment (before or after freezing) or line type (tolerant or sensitive). Of the 4550 differently expressed genes, 948 exhibited differential expression due to treatment within line or lines under freezing condition. Analysis of gene ontology found that these 948 genes were significantly enriched for binding functions (DNA binding, ATP binding, and metal ion binding), protein kinase activity, and peptidase activity. Based on their enrichment, literature support, and significant levels of differential expression, 30 of these 948 genes were selected for quantitative real-time PCR (qRT-PCR) validation. The validation confirmed our RNA-Seq-based findings, with squared correlation coefficients of 80% and 50% in the tolerance and sensitive lines, respectively. This study provided valuable resources for further studies to enhance understanding of the molecular mechanisms underlying maize early freezing response and enable targeted breeding strategies for developing varieties with superior frost resistance to achieve yield potential.
玉米起源于热带气候，随着种植范围扩大到世界大部分温带地区，它面临着巨大挑战。在这些地区，霜冻和低温是阻碍玉米充分发挥产量潜力的主要因素。在中国北方适应的30个优良玉米自交系中，我们鉴定出两个具有极端但相反冷冻耐受性水平的品系——高耐受性和高敏感性。在这两个品系的幼苗期，我们使用RNA测序来测量冷冻处理前后玉米全基因组转录组的变化。总共表达了19794个基因，其中4550个基因由于处理（冷冻前或冷冻后）或品系类型（耐受性或敏感性）而表现出差异表达。在4550个差异表达基因中，948个基因在冷冻条件下由于品系内处理而表现出差异表达。基因本体分析发现，这948个基因在结合功能（DNA结合、ATP结合和金属离子结合）、蛋白激酶活性和肽酶活性方面显著富集。基于它们的富集情况、文献支持以及显著的差异表达水平，从这948个基因中选择了30个进行定量实时PCR（qRT-PCR）验证。验证结果证实了我们基于RNA测序的发现，耐受性和敏感品系的平方相关系数分别为80%和50%。本研究为进一步研究提供了有价值的资源，以加深对玉米早期冷冻反应分子机制的理解，并制定有针对性的育种策略，培育具有卓越抗冻性的品种以实现产量潜力。
