Investigating the Association between Flowering Time and Defense in the Arabidopsis thaliana-Fusarium oxysporum Interaction

Rebecca Lyons,Anca Rusu,Jonathan Powell,Jiri Stiller,John M Manners,Kemal Kazan,Keqiang Wu

doi:10.1371/journal.pone.0127699

Abstract

Plants respond to pathogens either by investing more resources into immunity which is costly to development, or by accelerating reproductive processes such as flowering time to ensure reproduction occurs before the plant succumbs to disease. In this study we explored the link between flowering time and pathogen defense using the interaction between Arabidopsis thaliana and the root infecting fungal pathogen Fusarium oxysporum. We report that F. oxysporum infection accelerates flowering time and regulates transcription of a number of floral integrator genes, including FLOWERING LOCUS C (FLC), FLOWERING LOCUS T (FT) and GIGANTEA (GI). Furthermore, we observed a positive correlation between late flowering and resistance to F. oxysporum in A. thaliana natural ecotypes. Late-flowering gi and autonomous pathway mutants also exhibited enhanced resistance to F. oxysporum, supporting the association between flowering time and defense. However, epistasis analysis showed that accelerating flowering time by deletion of FLC in fve-3 or fpa-7 mutants did not alter disease resistance, suggesting that the effect of autonomous pathway on disease resistance occurs independently from flowering time. Indeed, RNA-seq analyses suggest that fve-3 mediated resistance to F. oxysporum is most likely a result of altered defense-associated gene transcription. Together, our results indicate that the association between flowering time and pathogen defense is complex and can involve both pleiotropic and direct effects.

Highlights

Plants are frequently attacked by pathogens and deploy chemical and structural barriers to defend themselves, diverting plant resources away from growth and development [1]
The bolting response of plants inoculated with high inoculum densities could not be assessed due to plant death, overall these data suggest that the host plant is reprogrammed to accelerate the transition to flowering upon F. oxysporum infection
To determine if an association could be found between flowering time and disease resistance, we obtained 83 publically available A. thaliana ecotypes in addition to the F. oxysporum susceptible ecotype Ty-0 [23] and assessed their response to F. oxysporum

Summary

Introduction

Plants are frequently attacked by pathogens and deploy chemical and structural barriers to defend themselves, diverting plant resources away from growth and development [1]. The Association between Flowering Time and Defense in Arabidopsis the plant survives to reproduce, the timing of the transition to flowering and the amplitude of the immune response are tightly regulated. Plants often respond to biotic stress by altering flowering time. Susceptible Arabidopsis plants infected by bacterial and oomycete pathogens flower earlier than uninoculated plants [2] while herbivory by the African cotton leafworm Spodoptera littoralis delays flowering in Brassica rapa [3]. Flowering time was recently shown to be dependent on soil properties and soil microbiota in a wild relative of Arabidopsis [4]

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