SCS7 is a fatty acid 2-hydroxylase required for the synthesis of inositol phosphorylceramide but is not essential for normal growth in Saccharomyces cerevisiae. Here, we demonstrate that the Colletotrichum siamense SCS7 homolog CsSCS7 plays a key role in hyphal growth. The CsSCS7 deletion mutant showed strong hyphal growth inhibition, small conidia, and marginally reduced sporulation and also resulted in a sharp reduction in the full virulence and increasing the fungicide sensitivity. The three protein domains (a cytochrome b5 domain, a transmembrane domain, and a hydroxylase domain) are important to CsSCS7 protein function in hyphal growth. The fatty acid assay results revealed that the CsSCS7 gene is important for balancing the contents of multiple mid-long- and short-chain fatty acids. Additionally, the retarded growth and virulence of C. siamense ΔCsSCS7 can be recovered partly by the reintroduction of homologous sequences from Magnaporthe oryzae and Fusarium graminearum but not SCS7 of S. cerevisiae. In addition, the spraying of C. siamense with naked CsSCS7-double-stranded RNA (dsRNAs), which leads to RNAi, increases the inhibition of hyphal growth and slightly decreases disease lesions. Then, we used nano material Mg-Al-layered double hydroxide as carriers to deliver dsRNA, which significantly enhanced the control effect of dsRNA, and the lesion area was obviously reduced. These data indicated that CsSCS7 is an important factor for hyphal growth and affects virulence and may be a potential control target in C. siamense and even in filamentous plant pathogenic fungi.IMPORTANCECsSCS7, which is homologous to yeast fatty acid 2-hydroxylase SCS7, was confirmed to play a key role in the hyphal growth of Colletotrichum siamense and affect its virulence. The CsSCS7 gene is involved in the synthesis and metabolism of fatty acids. Homologs from the filamentous fungi Magnaporthe oryzae and Fusarium graminearum can recover the retarded growth and virulence of C. siamense ΔCsSCS7. The spraying of double-stranded RNAs targeting CsSCS7 can inhibit hyphal growth and reduce the disease lesion area to some extent. After using nano material Mg-Al layered double hydroxide as carrier, the inhibition rates were significantly increased. We demonstrated that CsSCS7 is an important factor for hyphal growth and affects virulence and may be a potential control target in C. siamense and even in filamentous plant pathogenic fungi.
Keywords: Colletotrichum siamense; control target; fatty acid hydroxylase CsSCS7; hyphal growth factor.