低磷下小麦/蚕豆间作调控低分子量有机酸代谢途径的机理研究

Organic acids secretion induced by low phosphorus (P) plays important role in the activation of soil P. Wheat/faba bean intercropping is traditional cropping pattern widely distributing in the southwest of China. In previous studies, we found that wheat/faba bean intercropping increased organic acids exuded by roots, which promoted P availability in red soil rhizosphere and subsequently uptake and utilization by crops. However, it is still unclear that the relationship between P availability and metabolic mechanism inducing low molecular weight organic acids by low P under intercropping. In our project, the metabolic and transcriptomic profiles combined with LC-MS/MS and RNA-seq will be used to study the different metabolites and genes changes in faba/bean intercropping roots under low P, thereby building the metabolic and gene network diagram. By bioinformatic analysis, we want to find main low molecular weight organic acids regulated by intercropping under low P. Further combining with the content and secretion of these organic acids, key metabolic enzyme activity and expression levels of genes involved in metabolism and transport, we will clarify the regulatory mechanism of organic acid metabolism in wheat/faba bean intercropping under low P. These results will not only provides deeper understanding for crop response mechanism that grass/legume intercropping activates soil P, but also has important scientific significance and reference value to improve red soil P availability.

低磷诱导根系有机酸分泌在土壤磷活化上发挥着重要作用。小麦/蚕豆间作是广泛分布于我国西南地区的一项传统种植模式。我们前期研究证实小麦/蚕豆间作与单作相比可以通过增加根系低分子量有机酸的分泌，促进红壤根际磷的有效性及作物对磷的吸收利用。然而这一过程中，间作的磷养分优势与低磷诱导的低分子量有机酸代谢间的关系尚不清楚。本项目拟通过代谢组学中液相二级质谱（LC-MS/MS）联用的手段并结合RNA-seq转录组测序技术，研究低磷下间作根系差异代谢物和基因的变化，构建代谢和基因网络图。通过生物信息学分析，解析低磷下间作调控的主要差异低分子量有机酸种类，进一步结合主要有机酸含量与分泌量、代谢关键酶活性以及代谢与转运关键基因的表达水平，阐明小麦/蚕豆间作响应低磷的低分子量有机酸代谢调控机制，为禾本科/豆科间作活化磷的作物应答机制提供更深的理论认识，同时对促进红壤磷的高效利用具有重要的科学意义和参考。

低磷诱导根系有机酸分泌在土壤磷活化中发挥着重要作用。小麦//蚕豆间作是广泛分布于我国西南地区的一项传统种植模式。我们前期研究证实，小麦//蚕豆间作可通过增加根系低分子量有机酸分泌，提高红壤作物根际磷有效性及对磷的利用。然而，间作的磷养分优势与低分子量有机酸代谢间的关系尚不清楚。本项目采用水培实验模拟间作体系，综合运用植物营养学、生理与分子生物学手段，并结合田间验证，开展研究。主要研究结果如下：1）低磷下，小麦//蚕豆间作促进小麦草酸和苹果酸、蚕豆柠檬酸和苹果酸的分泌，从而提高磷的活化和有效性；2）低磷下，间作显著增加小麦和蚕豆的总根长、根表面积和根体积，增加小麦对磷的竞争比和积累量，最终提高小麦生物量和间作群体对磷的吸收；3）间作小麦显著上调脂质（特别是磷脂酰类化合物）、酚酸和黄酮化合物等次生代谢物的表达来促进植株在低磷下的生长和应答，其中柠檬酸和苹果酸的分泌量可能与体内的合成量成正相关；4）进一步利用低磷红壤上玉米//大豆田间定位试验对上述结果进行验证。玉米//大豆间作显著提高玉米产量和磷利用率，其间作优势在低磷供应（P60）下最为显著。P60显著增加间作玉米根际土壤活性磷和中活性磷的转化量，同时降低难溶性磷的转化量，其原因可能与P60下间作玉米根系草酸和苹果酸分泌量的增加有关（这与小麦的结果是一致的）。综上所述，本研究在可控条件下，初步阐明了小麦//蚕豆间作根-根系分泌物互作的生物学效应和机制，为揭示间作活化红壤磷提供了新的思路和依据。