Institute of Agricultural Biotechnology, Jilin Academy of Agricultural Sciences, Changchun 130033, Jilin, China.
College of Animal Science and Technology, Jilin Agricultural University, Changchun 130118, Jilin, China.
Gene. 2021 Jul 30;791:145714. doi: 10.1016/j.gene.2021.145714. Epub 2021 May 9.
Lead (Pb) is a serious heavy metal soil pollutant. It can be absorbed and accumulated by plant roots and impact plant growth. Medicago sativa L. (alfalfa) is a low-input forage and potential bioenergy crop, and improving its yield and quality has always been a focus of the alfalfa breeding industry. Little is known about the mechanism by which alfalfa responds to Pb stress at the molecular level. In this study, three alfalfa genotypes (a lead-resistant type (LR), a lead-sensitive type (LS) and an intermediate type (IN)) with contrasting abilities to resist lead were exposed to different durations of Pb treatment. Next-generation sequencing (NGS)-based RNA-seq technology was employed to characterize the root transcriptomes of three genotypes of alfalfa and identify differentially expressed genes (DEGs) during Pb stress. Genotypes LR and LS displayed different mechanisms of tolerance. In LR, the accumulation of more resistant substances was induced by the upregulation of sucrose synthase, glucan endo-1,3-beta-glucosidase, beta-amylase 3, probable trehalose-phosphate phosphatase J, 6-phosphofructo-2-kinase delta-1-pyrroline-5-carboxylate synthase (P5CS) and δ-ornithine aminotransferase (δ-OAT). In addition, flavin monooxygenase (YUCCA), 4-coumarate:CoA ligase-like protein (4CL), cinnamoyl-CoA reductase-like protein (CCR), ferulate 5-hydroxylase (F5H) and caffeic acid O-methyltransferase (COMT) were upregulated, leading to root development in a short time under Pb stress. Further study of the expression levels of metal transport-related genes, such as NRAMP (metal transporter), MATE (multidrug and toxin extrusion), HIPPs (heavy metal-associated isoprenylated plant proteins), MTP (metal tolerance protein), and ABC transporter, suggested that these genes were differentially expressed after lead treatment in the three alfalfa genotypes. Our research provides useful information for further studies on the molecular mechanism of Pb resistance in Medicago sativa L.
铅（Pb）是一种严重的重金属土壤污染物。它可以被植物根系吸收和积累，从而影响植物的生长。紫花苜蓿（Medicago sativa L.）是一种低投入的饲料和潜在的生物能源作物，提高其产量和质量一直是苜蓿育种行业的重点。目前，人们对紫花苜蓿在分子水平上对铅胁迫的反应机制知之甚少。在这项研究中，三种苜蓿基因型（耐铅型（LR）、敏感型（LS）和中间型（IN））在不同时间的 Pb 处理下，采用基于下一代测序（NGS）的 RNA-seq 技术来表征三种苜蓿基因型的根转录组，并鉴定 Pb 胁迫下差异表达基因（DEGs）。基因型 LR 和 LS 表现出不同的耐受机制。在 LR 中，通过蔗糖合酶、葡聚糖内切-1,3-β-葡糖苷酶、β-淀粉酶 3、可能的海藻糖-6-磷酸磷酸酶 J、6-磷酸果糖-2-激酶 delta-1-吡咯啉-5-羧酸合酶（P5CS）和 δ-鸟氨酸氨基转移酶（δ-OAT）的上调，诱导了更多抗性物质的积累。此外，黄素单加氧酶（YUCCA）、4-香豆酸：CoA 连接酶样蛋白（4CL）、肉桂酰-CoA 还原酶样蛋白（CCR）、阿魏酸 5-羟化酶（F5H）和咖啡酸 O-甲基转移酶（COMT）的上调，导致在 Pb 胁迫下，根在短时间内发育。进一步研究金属转运相关基因（如 NRAMP（金属转运蛋白）、MATE（多药和毒素外排）、HIPPs（重金属相关异戊二烯化植物蛋白）、MTP（金属耐受蛋白）和 ABC 转运蛋白）的表达水平表明，在三种苜蓿基因型中，这些基因在铅处理后差异表达。我们的研究为进一步研究紫花苜蓿耐铅的分子机制提供了有用的信息。
