Quarantin Alessandra, Glasenapp Anika, Schäfer Wilhelm, Favaron Francesco, Sella Luca
Dipartimento del Territorio e Sistemi Agro-Forestali (TESAF), Research Group in Plant Pathology, Università degli Studi di Padova, Viale dell'Università 16, 35020, Legnaro, Italy.
Biocenter Klein Flottbek, Molecular Phytopathology and Genetics, University of Hamburg, Hamburg, Germany.
Plant Physiol Biochem. 2016 Dec;109:220-229. doi: 10.1016/j.plaphy.2016.10.001. Epub 2016 Oct 4.
The genome of Fusarium graminearum, a necrotrophic fungal pathogen causing Fusarium head blight (FHB) disease of wheat, barley and other cereal grains, contains five genes putatively encoding for proteins with a cerato-platanin domain. Cerato-platanins are small secreted cysteine-rich proteins possibly localized in the fungal cell walls and also contributing to the virulence. Two of these F. graminearum proteins (FgCPP1 and FgCPP2) belong to the class of SnodProt proteins which exhibit phytotoxic activity in the fungal pathogens Botrytis cinerea and Magnaporthe grisea. In order to verify their contribution during plant infection and fungal growth, single and double gene knock-out mutants were produced and no reduction in symptoms severity was observed compared to the wild type strain on both soybean and wheat spikes. Histological analysis performed by fluorescence microscopy on wheat spikelets infected with mutants constitutively expressing the dsRed confirmed that FgCPPs do not contribute to fungal virulence. In particular, the formation of compound appressoria on wheat paleas was unchanged. Looking for other functions of these proteins, the double mutant was characterized by in vitro experiments. The mutant was inhibited by salt and HO stress similarly to wild type. Though no growth difference was observed on glucose, the mutant grew better than wild type on carboxymethyl cellulose. Additionally, the mutant's mycelium was more affected by treatments with chitinase and β-1,3-glucanase, thus indicating that FgCPPs could protect fungal cell wall polysaccharides from enzymatic degradation.
禾谷镰刀菌是一种引起小麦、大麦和其他谷物赤霉病的坏死性真菌病原体，其基因组包含五个推测编码具有角质素 - 悬铃木蛋白结构域的蛋白质的基因。角质素 - 悬铃木蛋白是一类小的、分泌型的富含半胱氨酸的蛋白质，可能定位于真菌细胞壁，并且也与毒力有关。这两种禾谷镰刀菌蛋白（FgCPP1和FgCPP2）属于SnodProt蛋白类别，在真菌病原体灰葡萄孢和稻瘟病菌中表现出植物毒性活性。为了验证它们在植物感染和真菌生长过程中的作用，构建了单基因和双基因敲除突变体，与野生型菌株相比，在大豆和小麦穗上均未观察到症状严重程度的降低。通过荧光显微镜对感染了组成型表达dsRed的突变体的小麦小穗进行组织学分析，证实FgCPPs对真菌毒力没有贡献。特别是，小麦内稃上复合附着胞的形成没有变化。为了寻找这些蛋白质的其他功能，通过体外实验对双突变体进行了表征。该突变体与野生型类似，受到盐和过氧化氢胁迫的抑制。虽然在葡萄糖上未观察到生长差异，但该突变体在羧甲基纤维素上比野生型生长得更好。此外，该突变体的菌丝体受几丁质酶和β - 1,3 - 葡聚糖酶处理的影响更大，因此表明FgCPPs可以保护真菌细胞壁多糖免受酶促降解。
