ICOM1 Abstract

ONLY TUESDAY SESSION 5 GENE EXPRESSION BLEE, KRISTOPHER A. & ANNE J. ANDERSON. Department of Biology, Utah State University, Logan, Utah, 84322-5305, USA. - A comparison of responses in bean roots to colonization by Glomus intraradices and Fusarium solani. Dark red kidney bean (Phaseolus vulgaris L. cv. Moncalm) roots were differentially colonized by pathogenic and beneficial fungi. The pathogenic F. solani f. sp. phaseoli grew inter- and intracellularly throughout the root cortex and penetrated the vascular cylinder. G. intraradices grew intercellularly until reaching certain cortical cells surrounding the endodermis which were penetrated and arbuscules formed within. Invading hyphae of F. solani f. sp. phaseoli autofluoresced yellow. Arbuscules of G. intraradices caused a pink autofluorescence and vesicles yellow. Whether the autofluorescence is due to plant or fungal cell wall components is not known. Accumulation of transcripts for defense-related proteins were detected differentially in roots colonized by the pathogenic and beneficial fungi. In situ hybridizations showed the arbusculated cortical cells responded with increased accumulations of transcripts for the defense-related enzymes phenylalanine ammonia-lyase and chitinase. Transcripts for two cell wall-associated proteins peroxidase (PER) and hydroxyproline-rich glycoprotein (HYP) were elevated in cells in contact with the pathogen. HYP but not PER transcripts were increased in arbusculated cells of mycorrhizal roots. PER transcript accumulation in the F. solani f. sp. phaseoli infected roots was not accompanied with lignification as detected by phloroglucinol-HCl staining.