Abstract
Oidium heveae B.A. Steinmann is a biotrophic fungus that infects rubber tree and causes powdery mildew disease, resulting in significant annual rubber yield losses worldwide. Researches on O. heveae in China had been limited on the cytological observation for the interaction of O. heveae with rubber tree, and the environment factors, such as temperature on the disease development. There had been scarce research on the infection mechanism of this important fungal pathogen at the molecular level. Pathogenicity-related genes of O. heveae are important for us to understand its infection process, which can potentially become targets for disease control. We have characterized eleven pathogenicity-related genes of O. heveae by genomics and transcriptomic studies. Four genes are involved in fungal metabolism, and the other three are related to fungal growth. Four genes were found to encode hypothetical proteins. The expression of these genes was further studied by qRT-PCR. Our results indicated that the expression of the metabolism-related Oh-PC2 gene encoding phosphoenolpyruvate carboxykinase (PEPCK) was up-regulated at 3 dpi (day post infection). Our data also demonstrated that at 3 dpi during the hyphae formation stage, the expression of all three fungal growth-related genes Oh-AAA-peroxin, Oh-RNP and Oh-Imp was up-regulated. Additionally, the expression of at least three O. heveae genes encoding hypothetical proteins was shown to increase at 3 dpi. Our results have provided novel insight to understanding the molecular mechanisms of O. heveae pathogenicity during its infection of rubber tree
Highlights
IntroductionA. Steinmann infects rubber tree and causes powdery mildew, a worldwide disease in the rubber tree belt
For the four genes involved in the metabolism pathway, we found that the expression of Oh (O. heveae)-EKA and Oh-GAP was not up-regulated at 1, 3 and 30 dpi (Figure 2A)
Little information is available on the gene functions of O. heveae
Summary
A. Steinmann infects rubber tree and causes powdery mildew, a worldwide disease in the rubber tree belt. O. heveae infection results in serious damage on the growth of rubber trees and significant economic loss in the rubber production. Cool and humid weather is favorable for powdery mildew disease outbreak on rubber trees. O. heveae is an obligate parasitic (biotrophic) fungus occurring on the leaf surface of rubber trees. The identification and classification of this fungus are still uncertain because there is no authoritative report of its morphology and no record of its teleomorphic stage [1,2]
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