基因组学在作物抗逆性研究中的新进展

自然环境中各种生物和非生物胁迫是影响作物产量的巨大威胁。随着现代分子生物学的发展,从分子水平研究作物抵御逆境的机理已成为生态农业研究的一个重要任务,分子遗传学与生态学的整合诞生了生态基因组学即用基因组学的技术和手段研究生态学领域的问题。基因组学按其研究内容分为功能基因组学、结构基因组学和比较基因组学,本文从这3方面分别阐述了作物抵抗生物胁迫和非生物胁迫的生态基因组学研究进展,总结了基因组学在植物抗逆性研究中的一些新技术和新手段,特别是基于近几年发展起来的二代深度测序所带来的一系列高通量的检测方法与结果。①功能基因组学包含转录组学、表观遗传学、蛋白组学、相互作用组学、代谢组学和表型组学,本文侧重从植物抗逆的功能基因表达水平上的研究展开,重点探讨了转录组学和表观遗传学在植物抗逆研究的新进展,介绍了一些转录组学和表观遗传学研究技术,如基因芯片技术、RNA测序技术、SAGE、cDNA-AFLP、SSH、亚硫酸盐法、ChIP-Chip、ChIP-seq等;例举了一些转录因子基因家族在植物抗逆反应中的作用,总结其作用共性,结果表明不少抗逆基因受到胁迫后基因转录激活上有一定相关性,大多受激素信号转导途径所调控,很多抗逆途径最终都涉及到ABA信号传导通路并与衰老相关;植物的抗逆性受多个信号通路调控,对同一逆境响应常常需要不同的转录因子共同参与,而同一转录因子也有可能参与2个以上的不同抗逆反应;表观遗传学则指在不改变基因序列前提下,对DNA甲基化修饰、组蛋白翻译后修饰及小RNA介导的信号传导等,有证据表明其存在遗传印记作用。②结构基因组学主要利用QTL定位和DNA测序技术,确定植物基因组的遗传图谱和物理图谱,二代深度测序平台的建立使许多植物的全基因组测序成为可能。迄今为止,已有超过40种植物完成全基因组测序,越来越多的植物全基因组计划正在实施中或预计实施。③比较基因组学是基于功能基因组学和结构基因组学进而比较不同物种或不同群体间的基因组差异和相关性的研究,可分析逆境响应相关基因在进化过程中及在地理位置分布中的作用和意义,也同时为QTL定位及功能基因组学研究提供丰富信息。此外,还简要介绍并列举了一些网络共享作物抗逆的生物信息资源数据库。虽然基因组学在如何正确处理海量数据等问题上还存在瓶颈,但它提供的大量作物抗逆方面的基因组信息已为植物抗逆研究提供了众多线索与依据,为今后改良作物抗逆性的遗传育种工作带来了新启示。

Advances in applications of genomics in stress resistance studies of crops

The continuous and excessive application of phosphorus (P) fertilizers and manure in intensive agricultural systems have led to soil P accumulation and progressive saturation of soil sorption capacity. This has significantly influenced soil P loss and P accumulation in aquatic ecosystems. The Taihu Lake Region of the Yangtse River Delta has for decades been a highly intensive agricultural production zone in China. Here, applications of chemical fertilizers and farmyard manure have been an effective method of improving soil fertility and productivity. Long-term applications of fertilizers and/or manure, often in excess of immediate plant uptake, have resulted in significant P accumulation and loss in this region. This has considerably increased the potential for eutrophication in the Taihu Lake. The change-point theory (with a soil Olsen-P content threshold above which the potential for significant P loss from soils to water systems occurred) has been considered to be scientific and useful in P management in agricultural soils. Up to date, however, there has been less report with respect to the Olsen-P change-point theory for paddy soils in the Taihu Lake Region. In this study, a long-term (13 years) P fertilization experiment in four P application doses (0 kg·hm^-2·a^-1, 30 kg·hm^-2·a^-1, 60 kg·hm^-2·a^-1 and 90 kg·hm^-2·a^-1) was conducted in the Taihu Lake Region to evaluate the accumulation of Olsen-P under rice-wheat rotation cropping system. The experiment evaluated the environmental risks caused by P loss from soils to water systems. Topsoil (0~15 cm), surface water and leachates (30 cm and 60 cm) Olsen-P and total P (TP) contents were determined. Furthermore, a split-line regression model was used to estimate the risks of P loss from soils to water bodies and the change-point of soil Olsen-P in the Taihu Lake Region determined. Although, TP concentrations in surface water bodies and in 30 cm leachate significantly increased with increasing application rate of fertilizer-P, no significant increase was observed in the 60 cm leachate. As the risk of P runoff was mainly in the first 9 days after fertilizer-P application, it was advisable to control paddy field drainage during this period. Split-line regression analysis suggested that the change-points of Olsen-P content in surface soil triggering P leaching and runoff were respectively 26.0 mg·kg^-1, 24.8 mg·kg^-1. Fertilizer-P application at 60 kg·hm^-2·a^-1 and 90 kg·hm^-2·a^-1 for 13 years resulted in respective soil Olsen-P accumulation of 26.9 mg·kg^-1 and 33.2 mg·kg^-1, which were all higher than the change-points. TP concentration of 30 cm leachate was also increased significantly. With continuous application of fertilizer-P at 30 kg·hm^-2·a^-1 for 13 years, soil Olsen-P content remained at (10.1±2.0) mg·kg^-1. This was sufficient for optimum rice/wheat growth without any risk of P loss. It was therefore not suitable to continuously apply 60 kg·hm^-2·a^-1 of fertilizer-P for a long time in paddy fields. The results demonstrated that intermittent fertilizer-P applications at 30 kg·hm^-2·a^-1 and 60 kg·hm^-2·a^-1 were suitable for rice-wheat rotation cropping system in the Taihu Lake Region.