Transcription of Biotic Stress Associated Genes in White Clover (Trifolium repens L.) Differs in Response to Cyst and Root-Knot Nematode Infection.

Afsana Islam,Michael T Mcmanus,Paul P Dijkwel,Susanna Leung,Chris F Mercer,John Jones

doi:10.1371/journal.pone.0137981

Afsana Islam, Michael T Mcmanus + Show 4 more

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https://doi.org/10.1371/journal.pone.0137981

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Journal: PloS one	Publication Date: Sep 22, 2015
Citations: 12	License type: CC BY 4.0

Affiliation: Massey University

Abstract

The transcription of four members of the Kunitz proteinase inhibitor (KPI) gene family of white clover (Trifolium repens L.), designated as Tr-KPI1, Tr-KPI2, Tr-KPI4 and Tr-KPI5, was investigated at both local infection (roots) and systemic (leaf tissue) sites in white clover in response to infection with the clover root knot nematode (CRKN) Meloidogyne trifoliophila and the clover cyst nematode (CCN) Heterodera trifolii. Invasion by the CRKN resulted in a significant decrease in transcript abundance of Tr-KPI4 locally at both 4 days post-infection (dpi) and at 8 dpi, and an increase in transcription of Tr-KPI1 systemically at 8 dpi. In contrast, an increase in transcript abundance of all four Tr-KPI genes locally at 4 and 8 dpi, and an increase of Tr-KPI1, Tr-KPI2, and Tr-KPI5 at 8 dpi systemically was observed in response to infection with the CCN. Challenge of a resistant (R) genotype and a susceptible (S) genotype of white clover with the CCN revealed a significant increase in transcript abundance of all four Tr-KPI genes locally in the R genotype, while an increase in abundance of only Tr-KPI1, Tr-KPI2, and Tr-KPI5 was observed in the S genotype, and only at 4 dpi. The transcript abundance of a member of the1-AMINOCYCLOPROPANE-1-CARBOXYLATE (ACC) SYNTHASE gene family from white clover (Tr-ACS1) was significantly down-regulated locally in response to CRKN infection at 4 and 8 dpi and at 4 dpi, systemically, while abundance increased locally and systemically at 8 dpi in response to CCN challenge. Conversely, the abundance of the jasmonic acid (JA) signalling gene, CORONATINE-INSENSITIVE PROTEIN 1 from white clover (Tr-COI1) increased significantly at 8 dpi locally in response to CRKN infection, but decreased at 8 dpi in response to CCN infection. The significance of this differential regulation of transcription is discussed with respect to differences in infection strategy of the two nematode species.

Highlights

The mechanisms of plant defence against herbivory and microbial pathogens can be broadly classified as constitutive or induced
To expand our study on the significance of the observed transcriptional changes that occur within the Tr-Kunitz proteinase inhibitor (KPI) gene family in response to nematode infection, we examined the transcript abundance of two key genes associated with biotic stress responses, including plant-nematode interactions
In response to clover root knot nematode (CRKN), the transcript abundance of all four Tr-KPI genes in the infected root tissue did not show any significant increase when compared with the control tissue (Fig 2A), but a significant increase (p = 0.010) in the abundance of Tr-KPI1 only was observed at 8 dpi in the remote first fully expanded (FFE) leaf tissue (Fig 2B)

Summary

Introduction

The mechanisms of plant defence against herbivory and microbial pathogens can be broadly classified as constitutive or induced. One of the most common inducible defences in plants against herbivory is the synthesis of proteinase inhibitors (PIs). One group of the serine PI superfamily are the Kunitz proteinase inhibitors (KPIs) which, where examined in plants, are widespread and generally exist as multi-gene families [4,5,6,7]. In common with the large PI families in plants, the KPIs have been shown to function as storage proteins and insect pest resistance factors [8,9,10,11], and have been used in transgenic approaches to confer protection against insect pests to the transformants [12,13,14,15,16]

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