Disease Resistance Gene-Induced Growth Inhibition Is Enhanced byrcd1Independent of Defense Activation in Arabidopsis      

Abstract

Activation of plant immune responses is often associated with an inhibition of plant growth. The molecular mechanisms underlying this fitness cost are unknown. Here, we utilize the autoimmune response mutant suppressor of npr1, constitutive1 (snc1) resulting from an activated form of the Disease Resistance (R) gene to dissect the genetic component mediating growth inhibition in Arabidopsis (Arabidopsis thaliana). The radical-induced cell death1 (rcd1) mutant defective in responses to reactive oxygen species (ROS) was isolated as an enhancer of the snc1 mutant in growth inhibition but not in defense response activation. Similarly, the vitamin C2 (vtc2) and vtc3 mutants defective in ROS detoxification enhanced the growth defects of snc1. Thus, perturbation of ROS status by R gene activation is responsible for the growth inhibition, and this effect is independent of defense response activation. This was further supported by the partial rescue of growth defects of rcd1 snc1 by the respiratory burst oxidase homolog D (rbohD) and rbohF mutations compromising the generation of ROS burst. Collectively, these findings indicate that perturbation of ROS homeostasis contributes to the fitness cost independent of defense activation.

Monoubiquitination of Histone 2B at the Disease Resistance Gene Locus Regulates Its Expression and Impacts Immune Responses in Arabidopsis

“…Fine tuning R gene expression is important for not only plant defense responses but also, balancing plant immunity, growth, and development. This is exemplified by the large impact of SNC1 expression on growth and immunity, because an increase of its transcript level leads to autoimmune responses and greatly reduced stature (Zhang et al, 2003;Yang and Hua, 2004;Yang et al, 2006;Li et al, 2010b;Zhu et al, 2013). In this study, we show that HUB1 directly modifies the chromatin of the SNC1 locus and regulates the expression of SNC1 and two other genes in the RPP5 gene cluster.…”

Should I fight or should I grow now? The role of cytokinins in plant growth and immunity and in the growth–defence trade-off

“…This existence of several physiological mechanisms that could account for growth-defence trade-offs stimulates one to hypothesize that growth suppression can be decoupled from defence activation. Studies that examine the fitness cost of defence have found that ROS produced during pathogen invasion are partly responsible for growth suppression independently of defence activation (Zhu et al, 2013).…”

Modernization in plant breeding approaches for improvingbiotic stress resistance in crop plants

“…In resistance conferring R genes, leucine rich repeats (LRRs) are present and a mutation in the RPS5 gene of Arabidopsis showed interaction of the LRR region with other plant proteins. The mutant rps5-1 resulted in replacement of lysine with glutamate amino acid in the LRR region and this altered plant response against downy mildew and bacteria (Warren et al, 1998;Huang et al, 2010;Zhu et al, 2013;Wang et al, 2014). In barley, the CNGC4 gene has 67% amino acid similarity with Arabidopsis based AtCNGC4, which is a disease resistance related gated ion channel.…”

“…The same effects of this mutation were recorded in model species Brachypodium distachyon and Hordeum vulgare, indicating the conservation of disease resistance mechanisms between both species. However, Zhu et al (2013) concluded that plant defense response activation compromised plant growth and development in Arabidopsis mutant radical-induced cell death1 (rcd1). The rcd1 showed disturbed reactive oxygen species (ROS) production in plants, which resulted in growth inhibition.…”