Clavibacter michiganensis Downregulates Photosynthesis and Modifies Monolignols Metabolism Revealing a Crosstalk with Tomato Immune Responses.

Dikran Tsitsekian,Gerasimos Daras,Dimitris Chatzopoulos,Stamatis Rigas,Theologos Koufakis,Dimitris Templalexis,Konstantinos Koudounas,Vardis Ntoukakis,Dimitris Malliarakis,Polydefkis Hatzopoulos,Konstantina Karamanou,Dimitris Goumas

doi:10.3390/ijms22168442

Abstract

The gram-positive pathogenic bacterium Clavibacter michiganensis subsp. michiganensis (Cmm) causes bacterial canker disease in tomato, affecting crop yield and fruit quality. To understand how tomato plants respond, the dynamic expression profile of host genes was analyzed upon Cmm infection. Symptoms of bacterial canker became evident from the third day. As the disease progressed, the bacterial population increased in planta, reaching the highest level at six days and remained constant till the twelfth day post inoculation. These two time points were selected for transcriptomics. A progressive down-regulation of key genes encoding for components of the photosynthetic apparatus was observed. Two temporally separated defense responses were observed, which were to an extent interdependent. During the primary response, genes of the phenylpropanoid pathway were diverted towards the synthesis of monolignols away from S-lignin. In dicots, lignin polymers mainly consist of G- and S-units, playing an important role in defense. The twist towards G-lignin enrichment is consistent with previous findings, highlighting a response to generate an early protective barrier and to achieve a tight interplay between lignin recomposition and the primary defense response mechanism. Upon progression of Cmm infection, the temporal deactivation of phenylpropanoids coincided with the upregulation of genes that belong in a secondary response mechanism, supporting an elegant reprogramming of the host transcriptome to establish a robust defense apparatus and suppress pathogen invasion. This high-throughput analysis reveals a dynamic reorganization of plant defense mechanisms upon bacterial infection to implement an array of barriers preventing pathogen invasion and spread.

Highlights

Tomato (Solanum lycopersicum) is an important vegetable of high economic value due to the taste, high yield and high content of beneficial to human health compounds [1].tomato plants are susceptible to various phytopathological agents of bacterial origin that compromise the yield and quality of the product
Bacterial growth in planta reached a maximum at 6 dpi, which was maintained until 12 dpi and the bacterial population gradually reduced to the initial levels of 3 dpi (Figure 1B)
ACO5 at both time points, contrary to the rest of the genes. These results indicate a strong and satisfactory correlation of quantitative realtime polymerase chain reaction (qRT-PCR) data with the outcome of transcriptome analysis, confirming the pattern of differentially expressed genes (DEGs) identified by RNA-seq analysis at both time points of tomato infection by Clavibacter michiganensis subsp. michiganensis (Cmm)

Summary

Introduction

Tomato (Solanum lycopersicum) is an important vegetable of high economic value due to the taste, high yield and high content of beneficial to human health compounds [1]. Tomato plants are susceptible to various phytopathological agents of bacterial origin that compromise the yield and quality of the product. Bacterial speck disease, caused by Pseudomonas syringae pv. Tomato (Pst), thrives in cool and moist environments causing severe growth defects [2]. Pst mostly affects the stems and leaves and is recognized by small, dark spots surrounded by a yellow ring. Bacterial spot affects the stems, leaves and fruits in wet and humid environments and causes loss of leaves due to various. Bacterial wilt is induced by the soil-borne bacterium Ralstonia solanacearum and results in leaf chlorosis leading to leaf loss. The entire plant suffers wilting [3]

Methods

Results

Conclusion