Alleviation of Phytophthora infestans Mediated Necrotic Stress in the Transgenic Potato (Solanum tuberosum L.) with Enhanced Ascorbic acid Accumulation.

Ill-Min Chung,Muthu Thiruvengadam,Chandrama Prakash Upadhyaya,Gurusaravanan Packiaraj,Govindasamy Rajakumar,Baskar Venkidasamy

doi:10.3390/plants8100365

Ill-Min Chung, Muthu Thiruvengadam + Show 4 more

Open Access

https://doi.org/10.3390/plants8100365

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Abstract

Potato is the most widely cultivated non-cereal crop in the world, and like any other crop, it is susceptible to yield losses because of various factors, including pathogen attacks. Among the various diseases of potato, late blight caused by the oomycete Phytophthora infestans is considered as the most devastating disease worldwide. In this study, transgenic potato plants overexpressing the D-galacturonic acid reductase (GalUR) gene with an enhanced level of cellular L-ascorbate (L-AsA) were challenged with Phytophthora infestans to determine the level of stress tolerance induced in those plants. With the onset of pathogen infection, necrotic lesions progressively expanded and became necrotic in the control plants. The transgenic potato lines with enhanced ascorbic acid showed reduced necrotic lesions. Hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels were relatively lower in transgenic plants compared to the untransformed control (UT) plants. The mRNA expressions of pathogenesis-related (PR) genes, such as pathogenesis related 1 (PR1) and phenylalanine ammonia-lyase (PAL) were slightly higher in GalUR overexpressing transgenic lines as compared to the untransformed control plants. Pathogen infection also altered the mRNA expression of genes associated with gibberellic acid (GA) and abscisic acid (ABA) biosynthesis. Furthermore, the increase in various antioxidant enzymes was also observed in the gene expression analysis with the transgenic plants. The complete loss of the pathogen growth and disease occurrence was not observed in our study; however, the findings indicated that an increase in the level of cellular L-ascorbate in the transgenic potato leads to enhanced cellular antioxidants, PR genes and plant defense hormones, such as GA and ABA resulting in the reduction of the disease symptoms caused by the Phytophthora infestans.

Highlights

Potato (Solanum tuberosum L.) stands as the world’s fourth largest grown non-cereal crop [1].Plant development and production of potatos are significantly affected by both abiotic and biotic stresses [2]
The disease symptom appeared quicker in untransformed control (UT) control plants as compared to the transgenic plants, probably due to the high antioxidant activity observed in the galacturonic acid reductase (GalUR) plants
This indicates that the increased antioxidant potential of GalUR expressing transgenic potato plants to the symptoms caused by P. infestans

Summary

Introduction

Potato (Solanum tuberosum L.) stands as the world’s fourth largest grown non-cereal crop [1].Plant development and production of potatos are significantly affected by both abiotic and biotic stresses [2]. In response to pathogen infection, plants trigger defense responses via the production of various reactive oxygen species (ROS), namely hydrogen peroxide (H2 O2 ), OH− , and O2 − molecules These ROS act as signals for the induction of a hypersensitive response (HR) mediated cell death and activation of defense associated genes to inhibit pathogen growth and their further spreading [3]. Vitamin C (L-ascorbic acid, AsA) is a significant multifunctional antioxidant compound and an important substrate for the detoxification of reactive oxygen species (ROS) involved in stress tolerance [7,8] It acts as a signaling molecule in several physiological processes such as cell division, growth regulation, and senescence [9,10]

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