Poloni Alana, Schirawski Jan
Albrecht-von-Haller Institute for Plant Sciences, Department for Molecular Biology of Plant-Microbe Interaction, Georg-August-University Göttingen, Julia-Lermontowa-Weg 3, 37077, Göttingen, Germany.
Institute of Applied Microbiology, Department of Microbial Genetics, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany.
Mol Plant Pathol. 2016 Jun;17(5):741-54. doi: 10.1111/mpp.12326. Epub 2015 Nov 11.
Smut fungi are biotrophic plant pathogens that exhibit a very narrow host range. The smut fungus Sporisorium reilianum exists in two host-adapted formae speciales: S. reilianum f. sp. reilianum (SRS), which causes head smut of sorghum, and S. reilianum f. sp. zeae (SRZ), which induces disease on maize. It is unknown why the two formae speciales cannot form spores on their respective non-favoured hosts. By fungal DNA quantification and fluorescence microscopy of stained plant samples, we followed the colonization behaviour of both SRS and SRZ on sorghum and maize. Both formae speciales were able to penetrate and multiply in the leaves of both hosts. In sorghum, the hyphae of SRS reached the apical meristems, whereas the hyphae of SRZ did not. SRZ strongly induced several defence responses in sorghum, such as the generation of H2 O2 , callose and phytoalexins, whereas the hyphae of SRS did not. In maize, both SRS and SRZ were able to spread through the plant to the apical meristem. Transcriptome analysis of colonized maize leaves revealed more genes induced by SRZ than by SRS, with many of them being involved in defence responses. Amongst the maize genes specifically induced by SRS were 11 pentatricopeptide repeat proteins. Together with the microscopic analysis, these data indicate that SRZ succumbs to plant defence after sorghum penetration, whereas SRS proliferates in a relatively undisturbed manner, but non-efficiently, on maize. This shows that host specificity is determined by distinct mechanisms in sorghum and maize.
黑粉菌是专性寄生的植物病原体，寄主范围非常狭窄。黑粉菌玉米丝轴黑粉菌存在两种适应寄主的专化型：引起高粱丝黑穗病的玉米丝轴黑粉菌高粱专化型（SRS），以及在玉米上致病的玉米丝轴黑粉菌玉米专化型（SRZ）。尚不清楚这两种专化型为何不能在各自不适合的寄主上形成孢子。通过真菌DNA定量分析和对染色植物样本的荧光显微镜观察，我们追踪了SRS和SRZ在高粱和玉米上的定殖行为。两种专化型都能够在两种寄主的叶片中穿透并繁殖。在高粱中，SRS的菌丝能够到达顶端分生组织，而SRZ的菌丝则不能。SRZ强烈诱导高粱产生多种防御反应，如过氧化氢、胼胝质和植保素的产生，而SRS的菌丝则不会。在玉米中，SRS和SRZ都能够通过植株扩散到顶端分生组织。对被侵染的玉米叶片进行转录组分析发现，SRZ诱导的基因比SRS诱导的更多，其中许多基因参与防御反应。在SRS特异性诱导的玉米基因中，有11个是五肽重复蛋白。结合显微镜分析，这些数据表明，SRZ在侵入高粱后因植物防御而败落，而SRS在玉米上以相对不受干扰的方式增殖，但效率不高。这表明寄主特异性是由高粱和玉米中不同的机制决定的。
