The alternative Medicago truncatula defense proteome of ROS—defective transgenic roots during early microbial infection

Abstract

ROP-type GTPases of plants function as molecular switches within elementary signal transduction pathways such as the regulation of ROS synthesis via activation of NADPH oxidases (RBOH-respiratory burst oxidase homolog in plants). Previously, we reported that silencing of the Medicago truncatula GTPase MtROP9 led to reduced ROS production and suppressed induction of ROS-related enzymes in transgenic roots (MtROP9i) infected with pathogenic (Aphanomyces euteiches) and symbiotic microorganisms (Glomus intraradices, Sinorhizobium meliloti). While fungal infections were enhanced, S. meliloti infection was drastically impaired. In this study, we investigate the temporal proteome response of M. truncatula MtROP9i transgenic roots during the same microbial interactions under conditions of deprived potential to synthesize ROS. In comparison with control roots (Mtvector), we present a comprehensive proteomic analysis using sensitive MS protein identification. For four early infection time-points (1, 3, 5, 24 hpi), 733 spots were found to be different in abundance: 213 spots comprising 984 proteins (607 unique) were identified after S. meliloti infection, 230 spots comprising 796 proteins (580 unique) after G. intraradices infection, and 290 spots comprising 1240 proteins (828 unique) after A. euteiches infection. Data evaluation by GelMap in combination with a heatmap tool allowed recognition of key proteome changes during microbial interactions under conditions of hampered ROS synthesis. Overall, the number of induced proteins in MtROP9i was low as compared with controls, indicating a dual function of ROS in defense signaling as well as alternative response patterns activated during microbial infection. Qualitative analysis of induced proteins showed that enzymes linked to ROS production and scavenging were highly induced in control roots, while in MtROP9i the majority of proteins were involved in alternative defense pathways such as cell wall and protein degradation.

AtROP6 is involved in reactive oxygen species signaling in response to iron‐deficiency stress in Arabidopsis thaliana

“…And in our study the total iron content of roots and leaves in both mutant and ROP6-overexpressed plants were not significantly changed compared with WT, but the downward trend of active iron content of leaves in the rop6 mutant showed that AtROP6 or ROS may be involved in iron distribution from roots to shoots. Furthermore, the silencing of the Medicago truncatula GTPase MtROP9 led to reduced ROS production while it suppressed induction of ROS-related enzymes [51]. These observations are consistent with our own observation of a markedly decreased accumulation of ROS and H 2 O 2 under Fe starvation in the rop6 mutant (Fig.…”

RNA-seq Transcriptome Response of Flax (Linum usitatissimum L.) to the Pathogenic Fungus Fusarium oxysporum f. sp. lini

“…From 14 transcripts matching MLPs, 11 were consistently repressed (Supplementary Figure S5V). Although the function of these proteins has not been completely elucidated, there is evidence of their regulation through hormone signaling (Ruperti et al, 2002; Yang et al, 2015; Wang et al, 2016), and activation in response to pathogens (Schenk et al, 2000; Kiirika et al, 2014; Yang et al, 2015). However, our results were opposite to these studies and we found only one study were 16 major latex proteins were repressed in response to oxidative stress in Arabidopsis (Stanley Kim et al, 2004).…”

Chickpea-Fusarium oxysporum interaction transcriptome reveals differential modulation of plant defense strategies

“…We found that several transcripts associated with ABA synthesis, degradation and signal transduction were also up-regulated in DVI, which indicated their key roles in chickpea defense. Transcripts for several pathogenesis related proteins, Major latex proteins 40 , auxin binding proteins 41 , etc. from ‘biotic and abiotic stress response’ category were detected with higher abundance and elevated expression in DVI.…”