The Histological, Effectoromic, and Transcriptomic Analyses of Solanum pinnatisectum Reveal an Upregulation of Multiple NBS-LRR Genes Suppressing Phytophthora infestans Infection.

Biao Gu,Xiaoli Cao,Hua Zhao,Qin Chen,Qinhu Wang,Wei Liu,Xiaoli Zhou,Zhaodan Chen

doi:10.3390/ijms21093211

Abstract

Utilization of disease resistance components from wild potatoes is a promising and sustainable approach to control Phytophthora blight. Here, we combined avirulence (Avr) genes screen with RNA-seq analysis to discover the potential mechanism of resistance in Mexican wild potato species, Solanum pinnatisectum. Histological characterization displayed that hyphal expansion was significantly restricted in epidermal cells and mesophyll cell death was predominant, indicating that a typical defense response was initiated in S. pinnatisectum. Inoculation of S. pinnatisectum with diverse Phytophthora infestans isolates showed distinct resistance patterns, suggesting that S. pinnatisectum has complex genetic resistance to most of the prevalent races of P. infestans in northwestern China. Further analysis by Avr gene screens and comparative transcriptomic profiling revealed the presence and upregulation of multiple plant NBS-LRR genes corresponding to biotic stresses. Six NBS-LRR alleles of R1, R2, R3a, R3b, R4, and Rpi-smira2 were detected, and over 60% of the 112 detected NLR proteins were significantly induced in S. pinnatisectum. On the contrary, despite the expression of the Rpi-blb1, Rpi-vnt1, and Rpi-smira1 alleles, fewer NLR proteins were expressed in susceptible Solanum cardophyllum. Thus, the enriched NLR genes in S. pinnatisectum make it an ideal genetic resource for the discovery and deployment of resistance genes for potato breeding.

Highlights

Potatoes, one of the most important food crops, have been affected by late blight disease for nearly 180 years [1]
In order to determine the susceptibility of the wild potato species S. pinnatisectum to infection by P. infestans, zoospore inoculation was performed with an aggressive isolate, Pi21366, which is
Compared to other wild potato species, very few novel R genes or functional homologues have been identified from S. pinnatisectum in the last two decades, but this Mexican wild potato species

Summary

Introduction

One of the most important food crops, have been affected by late blight disease for nearly 180 years [1]. To decrease the yield losses caused by Phytophthora infestans, cultivars of Solanum tuberosum expressing diverse resistance (R) genes have been developed and extensively applied in potato growing areas worldwide. Many typical R genes, such as R1 to R11 from Solanum demissum, were initially demonstrated to be successful in improving disease-resistant commercial potatoes. The R-gene-insensitive strains of P. infestans frequently emerged after large-scale application of resistant cultivars harboring major R genes [2,3]. More aggressive P. infestans isolates escaping recognition by R1-R11 genes were reported worldwide [4,5]. The outstanding disease-free phenotypes and long-term stability of R genes remain valuable, stimulating numerous attempts to discover natural immune receptors from Solanum species for potato resistance breeding [6,7]

Methods

Results

Conclusion