Leucine Regulates Zoosporic Germination and Infection by Phytophthora erythroseptica

Abstract

Pink rot (Phytophthora erythroseptica) of potato is a major concern in many potato production regions. The pathogen produces zoospores that serve as a primary inoculum for infection. To understand how the pink rot incidence is related to pathogen population, qualitative, and quantitative chemical analyses were conducted. It was demonstrated that P. erythroseptica zoospores required a minimal population of 103 zoospores/ml (threshold) for initiating germination and the subsequent infection; the percentage of zoosporic germination was positively correlated with the density of zoospores above the threshold. To elucidate the density-dependent behavior, zoospore exudate (ZE) was extracted from high-density (105/ml) zoospore suspension. Zoosporic inocula of P. erythroseptica at different concentrations were inoculated on potato tubers. Necrotic lesions were caused by inoculum with 100 zoospores per inoculation site; 5 zoospores per site did not cause lesions on the tuber. However, five zoospores did cause lesions when they were placed in ZE, suggesting ZE contained chemical compounds that regulate germination of zoospores. ZE was collected and analyzed using liquid chromatography mass spectroscopy (LC-MS). Results showed that the amino acid leucine was associated with zoosporic germination. Therefore, zoosporic germination and infection of P. erythroseptica were mediated by signaling molecules secreted from zoospores.

Comparative Genome Analysis Across 128 Phytophthora Isolates Reveal Species-Specific Microsatellite Distribution and Localized Evolution of Compartmentalized Genomes

“…CAG and AAG codes for leucine amino acid. It has been reported that amino acid leucine helps in zoospore germination, which eventually helps in the establishment of infection to the host of Phytophthora ( Jiang et al, 2019 ). Thus, SSRs with leucine CDS may have a vital role in germination, but further in-depth study is required for establishing this link.…”

Zoospore exudates from Phytophthora nicotianae affect immune responses in Arabidopsis

“…Zoospore exudates of Phytophthora have been shown as chemical signals for Phytophthora quorum sensing leading to zoospore aggregation, homing and infection initiation as well as communications between zoosporic oomycetes and with bacteria [3, 5, 7, 39, 42]. This study reveals new roles of zoospore exudates as virulence factors of the pathogen and inducers of plant immunity, contributing to the success of plant infection by Phytophthora zoospores.…”

“…This pathogen can use exudates from zoospores and bacteria to promote successful infection [3, 5, 6]. The exudates from zoospores of Phytophthora and Pythium , termed zoospore-free fluids (ZFF), function as quorum-sensing signals promoting zoospore homing and triggering infection by single zoospores [3, 5, 7]. However, it is not clear whether ZFF also affects plant immunity.…”

Comparison of growth, viability, sporulation, and virulence of Phytophthora capsici isolated from black pepper (Piper nigrum L.) on various media.

“…Then, each mycelium colony of P. capsici from each medium was stored at room temperature for 40 days. This aims to see the ability of the mycelium to grow again after being stored in the [8][8] media for 40 days. After 40 days of storage, the diameter of the mycelium of P. capsici was measured again for 6 days to determine the effectiveness of the seven media on mycelium growth.…”