Transcription Factor CfSte12 of Colletotrichum fructicola Is a Key Regulator of Early Apple Glomerella Leaf Spot Pathogenesis

Abstract

Glomerella leaf spot (GLS), caused by Colletotrichum fructicola, is a rapidly emerging disease leading to defoliation, fruit spot and storage fruit rot on apple in China. Little is known about the mechanisms of GLS pathogenesis. Early transcriptome analysis revealed that expression of the zinc finger transcription factor CfSte12 gene in C. fructicola was up-regulated in appressoria and leaf infection. To investigate functions of CfSte12 during pathogenesis, we constructed gene deletion mutants (ΔCfSte12) by homologous recombination. Phenotypic analysis revealed that CfSte12 was involved in pathogenesis of non-wounded apple fruit and leaf, as well as wounded apple fruit. Subsequent histological studies revealed that loss of pathogenicity by ΔCfSte12 on apple leaf was expressed as defects of conidium germination, appressorium development and appressorium-mediated penetration. Further RNA sequencing-based transcriptome comparison revealed that CfSte12 modulates the expression of genes related to appressorium function (e.g. the tetraspanin PLS1, Gas1-like proteins, cutinases, melanin biosynthesis genes) and candidate effectors likely involved in plant interaction. In sum, our results demonstrated that CfSte12 is a key regulator of early apple GLS pathogenesis in C. fructicola. Besides, CfSte12 is also needed by sexual development of perithecia and ascospores. Importance Glomerella leaf spot (GLS) is an emerging fungal disease of apple that causes huge economic losses in Asia, North America and South America. The damage inflicted by GLS manifests in rapid necrosis of leaves, severe defoliation and necrotic spot on fruit surface. However, few studies have addressed mechanisms of GLS pathogenesis. In this study, we identified and characterized a key pathogenicity-related transcription factor, CfSte12, of Colletotrichum fructicola that contributes to GLS pathogenesis. We provided evidence that the CfSte12 protein regulates many important pathogenic processes of GLS, including conidium germination, appressorium formation, appressorium-mediated penetration, and colonization. CfSte12 also impacts development of structures needed for sexual reproduction which are vital for the GLS disease cycle. These results revealed a key pathogenicity-related transcription factor CfSte12 in C. fructicola that causing GLS.

Fus3/Kss1‐MAP kinase and Ste12‐like control distinct biocontrol‐traits besides regulation of insect cuticle penetration via phosphorylation cascade in a filamentous fungal pathogen

“…Besides regulating cuticle penetration of and/or cell wall integrity together, Bbmpk1 and BbSte12 played different roles in control of growth, conidiogenesis and cell cycle, and osmotic and oxidative stress response. Different functions of Fus3/Kss1 MAPK homolog and Ste12-like in fungal development and differentiation are also examined in other fungal pathogens, 11,12,15,16,24,[26][27][28][29] suggesting that the two factors also participate in separate signaling pathway networks for mediation of different cellular/biological processes. Fus3/Kss1 MAPK homolog admittedly control different transcription factors, i.e., Pmk1 MAPK pathway phosphorylates a homeobox TF Hox7 besides Mst12, that regulates major physiological changes required for appressorium development-involved genes and some virulence-related genes in Magnaporthe oryzae.…”

“…23 Whereas, distinct roles of, Fus3/Kss1-MAPK and Ste12-like in fungal development and differentiation are demonstrated in some fungal pathogens (Supporting Information, Table S5). 11,12, [22][23][24][25][26][27][28][29] However, it is unclear what target genes are controlled by the MAPK and/or Ste12-like that are required for regulation of cuticle penetration/pathogenicity, and virulence-associated traits.…”

Selection of potential reference genes for RT-qPCR in the plant pathogenic fungus Colletotrichum fructicola

“…In evaluating reference genes, the results of normalization of target genes by CfRrp are consistent with the transcriptome data. In previous studies of C. fructicola gene expression, housekeeping genes such as Act and Tub are often used to normalize ( Liang et al, 2019 ; Song et al, 2019 ; Liu et al, 2021 ). CfAct and CfTub were not stable under the conditions set in this study, and the results were slightly different from transcriptome data after normalizing the target genes.…”

Evidences of Colletotrichum fructicola Causing Anthracnose on Passiflora edulis Sims in China

“…Previous studies have demonstrated C. fructicola as the causal organism causing anthracnose of fruit, vegetables, and economic crops, including chili [23], pear [24], apple [25], strawberry [26], dragon fruit [27], and tea [28]. Numerous studies have pointed out various ways to control anthracnose caused by Colletotrichum spp., including, but not limited to, the application of biorational pesticides, such as essential oil [29], biocontrol strategies [30], synthetic fungicides, and heat treatments [31].…”