Petitot Anne-Sophie, Kyndt Tina, Haidar Rana, Dereeper Alexis, Collin Myriam, de Almeida Engler Janice, Gheysen Godelieve, Fernandez Diana
Institut de Recherche pour le Développement, UMR 186 IPME (IRD-UM2-Cirad) 911, avenue Agropolis, BP 64501 34394 Montpellier Cedex 5, France.
Department of Molecular Biotechnology, Ghent University, Coupure links 653, 9000 Gent, Belgium.
Ann Bot. 2017 Mar 1;119(5):885-899. doi: 10.1093/aob/mcw256.
The root-knot nematode Meloidogyne graminicola is responsible for production losses in rice ( Oryza sativa ) in Asia and Latin America. The accession TOG5681 of African rice, O. glaberrima , presents improved resistance to several biotic and abiotic factors, including nematodes. The aim of this study was to assess the cytological and molecular mechanisms underlying nematode resistance in this accession.
Penetration and development in M. graminicola in TOG5681 and the susceptible O. sativa genotype 'Nipponbare' were compared by microscopic observation of infected roots and histological analysis of galls. In parallel, host molecular responses to M. graminicola were assessed by root transcriptome profiling at 2, 4 and 8 d post-infection (dpi). Specific treatments with hormone inhibitors were conducted in TOG5681 to assess the impact of the jasmonic acid and salicylic acid pathways on nematode penetration and reproduction.
Penetration and development of M. graminicola juveniles were reduced in the resistant TOG5681 in comparison with the susceptible accession, with degeneration of giant cells observed in the resistant genotype from 15 dpi onwards. Transcriptome changes were observed as early as 2 dpi, with genes predicted to be involved in defence responses, phenylpropanoid and hormone pathways strongly induced in TOG5681, in contrast to 'Nipponbare'. No specific hormonal pathway could be identified as the major determinant of resistance in the rice-nematode incompatible interaction. Candidate genes proposed as involved in resistance to M. graminicola in TOG5681 were identified based on their expression pattern and quantitative trait locus (QTL) position, including chalcone synthase, isoflavone reductase, phenylalanine ammonia lyase, WRKY62 transcription factor, thionin, stripe rust resistance protein, thaumatins and ATPase3.
This study provides a novel set of candidate genes for O. glaberrima resistance to nematodes and highlights the rice- M. graminicola pathosystem as a model to study plant-nematode incompatible interactions.
根结线虫稻根结线虫（Meloidogyne graminicola）导致亚洲和拉丁美洲的水稻（Oryza sativa）减产。非洲栽培稻（O. glaberrima）种质TOG5681对包括线虫在内的多种生物和非生物因素具有更强的抗性。本研究旨在评估该种质对线虫抗性的细胞学和分子机制。
通过对受感染根的显微镜观察和虫瘿的组织学分析，比较了稻根结线虫在TOG5681和感病的水稻基因型‘日本晴’中的侵入和发育情况。同时，通过感染后2、4和8天（dpi）的根转录组分析评估宿主对稻根结线虫的分子反应。在TOG5681中进行了激素抑制剂的特定处理，以评估茉莉酸和水杨酸途径对线虫侵入和繁殖的影响。
与感病种质相比，抗性种质TOG5681中稻根结线虫幼虫的侵入和发育减少，从15 dpi起在抗性基因型中观察到巨型细胞退化。早在2 dpi就观察到转录组变化，与‘日本晴’相比，预测参与防御反应、苯丙烷类和激素途径的基因在TOG5681中强烈诱导。在水稻 - 线虫不亲和相互作用中，没有特定的激素途径可被确定为抗性的主要决定因素。根据其表达模式和数量性状位点（QTL）位置鉴定了TOG5681中被认为参与抗稻根结线虫的候选基因，包括查尔酮合酶、异黄酮还原酶、苯丙氨酸解氨酶、WRKY62转录因子、硫堇、条锈病抗性蛋白、甜蛋白和ATPase3。
本研究为非洲栽培稻抗线虫提供了一组新的候选基因，并突出了水稻 - 稻根结线虫病理系统作为研究植物 - 线虫不亲和相互作用的模型。
