Volatile compounds from soilborne pathogenic Fungi affect plant growth and enhance plant biotic and abiotic stress resistance
Open Access
- Author:
- Bitas, Vasileios
- Graduate Program:
- Plant Pathology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- July 28, 2014
- Committee Members:
- Seogchan Kang, Dissertation Advisor/Co-Advisor
Seogchan Kang, Committee Chair/Co-Chair
Kathleen Marie Brown, Committee Member
Maria Del Mar Jimenez Gasco, Committee Member
Gretchen Anna Kuldau, Committee Member
David Michael Geiser, Committee Member - Keywords:
- Fusarium oxysporum
Verticillium
volatile compounds
Arabidopsis
growth promotion
auxin
root
stress resistance - Abstract:
- Diverse uses of volatile compounds as semio-chemicals for organismal and organism-environment interactions have been observed in a wide range of organisms. Results from recent studies of growth promoting rhizobacterial and biocontrol microorganisms have demonstrated that those organisms emit volatile compounds that promote growth and enhance biotic and abiotic stress resistance of plants. However, very little is known about if and how volatiles emitted by soilborne pathogenic fungi affect neighboring plants. The main goal of this thesis is studying how volatile compounds emitted by the soilborne fungi Fusarium oxysporum and Verticillium spp. affect Arabidopsis thaliana and Nicotiana tabacum in growth and stress resistance. First, known and suspected roles of microbial volatiles and their mechanisms of action, with the focus on their roles in affecting plant growth and stress resistance, have been reviewed (Chapter 1). A large number of F. oxysporum isolates, from diverse geographical locations and plant sources, have been screened for their ability to promote Arabidopsis growth (Chapter 2). The majority of the isolates produced volatiles that augmented Arabidopsis biomass, signifying that volatile-mediated growth promotion is a common trait for F. oxysporum. Further experiments with selected F. oxysporum isolates revealed that their volatiles instigate morphological and physiological alterations in A. thaliana and N. tabacum. Employment of A. thaliana phytohormone signaling mutants and a transgenic line expressing GUS under the DR5 promoter revealed that volatile-mediated biomass augmentation is regulated through manipulation of root auxin transport and perception. These results are similar to previous findings regarding bacterial volatile-mediated growth promotion and suggest that soilborne bacteria and fungi associated with plant roots potentially share a mechanism to manipulate neighboring plants. Chapter 3 concerns the effect that F. oxysporum volatiles have on plant resistance to biotic stress. Infection of A. thaliana with Pseudomonas syringae pv. tomato DC3000 after exposure to F. oxysporum volatiles showed volatile-mediated increased disease resistance. Pathogenicity assays with a transgenic A. thaliana line containing PR1::GUS, GUS under the control of the salicylic acid (SA) PR1 gene promoter, suggested that F. oxysporum volatiles prime SA-dependent induced systemic resistance. Volatiles from F. oxysporum also increased salinity tolerance in A. thaliana (Chapter 4). Chapter 5 outlines preliminary data on the effects of volatiles produced by Verticillium spp. on plant growth. Verticillium volatiles augmented growth of A. thaliana and N. tabacum in a manner similar to that caused by F. oxysporum volatiles. In conclusion, results shown in this thesis suggest that microbial volatile-mediated manipulation of plants represents a possibly conserved mechanism utilized by many root-associated microorganisms and is not an exclusive trait of beneficial microbes.