CSIRO, Agriculture and Food, Canberra, ACT 2601, Australia.
Australian Research Council Centre of Excellence in Plant Energy Biology, School of Agriculture, Food and Wine, University of Adelaide, Urrbrae, SA 5064, Australia.
Plant Physiol. 2023 May 31;192(2):1254-1267. doi: 10.1093/plphys/kiad104.
Many disease resistance genes in wheat (Triticum aestivum L.) confer strong resistance to specific pathogen races or strains, and only a small number of genes confer multipathogen resistance. The Leaf rust resistance 67 (Lr67) gene fits into the latter category as it confers partial resistance to multiple biotrophic fungal pathogens in wheat and encodes a Sugar Transport Protein 13 (STP13) family hexose-proton symporter variant. Two mutations (G144R, V387L) in the resistant variant, Lr67res, differentiate it from the susceptible Lr67sus variant. The molecular function of the Lr67res protein is not understood, and this study aimed to broaden our knowledge on this topic. Biophysical analysis of the wheat Lr67sus and Lr67res protein variants was performed using Xenopus laevis oocytes as a heterologous expression system. Oocytes injected with Lr67sus displayed properties typically associated with proton-coupled sugar transport proteins-glucose-dependent inward currents, a Km of 110 ± 10 µM glucose, and a substrate selectivity permitting the transport of pentoses and hexoses. By contrast, Lr67res induced much larger sugar-independent inward currents in oocytes, implicating an alternative function. Since Lr67res is a mutated hexose-proton symporter, the possibility of protons underlying these currents was investigated but rejected. Instead, currents in Lr67res oocytes appeared to be dominated by anions. This conclusion was supported by electrophysiology and 36Cl- uptake studies and the similarities with oocytes expressing the known chloride channel from Torpedo marmorata, TmClC-0. This study provides insights into the function of an important disease resistance gene in wheat, which can be used to determine how this gene variant underpins disease resistance in planta.
许多小麦（Triticum aestivum L.）中的抗病基因赋予了其对特定病原菌的强抗性，只有少数基因赋予了多病原体抗性。叶锈病抗性 67（Lr67）基因属于后者，因为它赋予了小麦对多种生物病原体的部分抗性，并编码了一个糖转运蛋白 13（STP13）家族己糖-质子同向转运体变体。抗性变体 Lr67res 中的两个突变（G144R、V387L）使其与敏感的 Lr67sus 变体区分开来。Lr67res 蛋白的分子功能尚不清楚，本研究旨在为此主题提供更多的知识。使用非洲爪蟾卵母细胞作为异源表达系统，对小麦 Lr67sus 和 Lr67res 蛋白变体进行了生物物理分析。用 Lr67sus 注射的卵母细胞表现出与质子偶联糖转运蛋白相关的特性，包括葡萄糖依赖性内向电流、Km 值为 110±10µM 葡萄糖和允许戊糖和己糖运输的底物选择性。相比之下，Lr67res 在卵母细胞中诱导了更大的糖非依赖性内向电流，暗示了一种替代功能。由于 Lr67res 是一个突变的己糖-质子同向转运体，因此研究了质子是否是这些电流的基础，但被否定了。相反，Lr67res 卵母细胞中的电流似乎主要由阴离子主导。这一结论得到了电生理学和 36Cl-摄取研究的支持，并且与表达已知的来自 Torpedo marmorata 的氯离子通道，TmClC-0 的卵母细胞相似。本研究为小麦中一个重要抗病基因的功能提供了深入的了解，这可用于确定该基因变体如何在植物中支撑抗病性。
