F-actin localization dynamics during appressorium formation in Colletotrichum graminicola

ABSTRACT

Appressoria are essential penetration structures for many phytopathogenic fungi. Here F-actin localization dynamics were documented during appressorium formation in vitro and in planta in Colletotrichum graminicola. Four discernible stages of dynamic F-actin distribution occurring in a programmed order were documented from differentiation of appressoria to formation of penetration pores: (stage A) from germ tube enlargement to complete expansion of the appressorium; (stage S) septation occurs; (stage L) a long period of low F-actin activity; (stage P) the penetration pore forms. The F-actin subcellular localization corresponded to each stage. A distinct redistribution of actin cables occurred at the transition from stage A to stage S. The in planta assays revealed that F-actin also assembled in invasive hyphae and that actin cables might play an essential role for penetration-peg development. The F-actin localization distribution may be used as a subcellular marker to define the developmental stages during appressorium formation.

• actin
• anthracnose
• appressorium
• Lifeact
• maize
• penetration peg

Acknowledgments

We thank Drs Nick D. Read, Adokiye Berepiki and Alexander Lichius for providing the Lifeact-GFP vectors. We thank Dr Lisa Vaillancourt for sharing wild-type C. graminicola strains and Dr Mike Kolomiets for providing maize seeds. We also thank Ms Talisa M.D. Rodriquez for assisting with experiments documented in Supplementary fig. 1 during her summer REU internship. This study was financially supported by USDA ( USDA-CSREES NRICGP 2007-35319-18334) and the Department of Plant Pathology and Microbiology, Texas A&M University.