Defense strategies against sweet potato chlorotic stunt and pakakuy virus coinfection unraveled

Abstract

This study into the response of two Ipomoea batatas (L.) Lam cultivars, Melinda and Tio Joe, to coinfection with sweet potato chlorotic stunt virus (SPCSV) and sweet potato pakakuy virus (SPPV), employed a comprehensive approach encompassing symptomatology, real-time quantitative polymerase chain reaction, metagenomics, and transcriptomics. SPCSV is a quarantine virus with synergistic effects, which decimate yields. SPPV is the most prevalent DNA virus in sweet potato germplasm, with a tendency to persist in meristems, posing a significant risk for germplasm transfer between territories. Graft inoculation experiments revealed that while Tio Joe remained asymptomatic for 12 weeks and suppressed virus replication, Melinda displayed symptoms early on and exhibited high virus titers. Metagenomic analyses corroborated these observations and confirmed that SPCSV and SPPV were responsible. Transcriptomic analysis unveiled disparities in gene expression between Melinda and Tio Joe. Differential gene expression was heightened and altered in Melinda as the viruses disrupted its gene expression. Its defense strategies, such as inducing abscisic acid signaling, were insufficient to overcome disruptive viral effects like oxidative stress, rendering it susceptible. In contrast, Tio Joe had relatively stable differential gene expression, indicating resistance to SPPV–SPCSV coinfection. Overexpressed genes such as sirtuin, rapid alkalization factor, and nuclear pore anchor triggered quantitative resistance, supported with enriched organelles such as mitochondrion and pathways such as proteasome and cutin, suberine, and wax biosynthesis. Tio Joe maintained its genome integrity and inhibited viral replication by tightly controlling gene expression and preventing reactive oxygen species accumulation.