CATALASE2 Coordinates SA-Mediated Repression of Both Auxin Accumulation and JA Biosynthesis in Plant Defenses

Abstract

Plants defend against pathogen attack by modulating auxin signaling and activating the salicylic acid (SA) and jasmonic acid (JA) signaling pathways. SA and JA act antagonistically in resistance to specific pathogen types, yet how plants coordinate these phytohormones remains elusive. Here we report that biotrophic-pathogen-induced SA accumulation dampens both auxin and JA synthesis by inhibiting CATALASE2 (CAT2) activity in the model plant Arabidopsis. SA suppression of CAT2 results in increased HO levels and subsequent sulfenylation of tryptophan synthetase β subunit 1, thus depleting the auxin biosynthetic precursor tryptophan. In addition, we find that CAT2 promotes JA biosynthesis by facilitating direct interaction of the JA biosynthetic enzymes ACX2 and ACX3, and thus SA repression of CAT2 inhibits JA accumulation. As such, the cat2-1 mutant exhibits increased resistance to biotrophic pathogens and increased susceptibility to necrotrophic pathogens. Our study illustrates how CAT2 coordinates SA repression of auxin accumulation and JA biosynthesis in plant defense.

Nucleoredoxin guards against oxidative stress by protecting antioxidant enzymes

“…The full extent to which catalase activity contributes to plant immune responses has only recently come to light. Catalases have previously been reported to bind SA, and a recent study showed that SA-induced suppression of CAT2 activity increased H 2 O 2 levels upon pathogen infection (21). Here we show that additionally, during oxidative stress and pathogen infection, CAT2 activity is regulated by NRX1.…”

Redox and the circadian clock in plant immunity: A balancing act

“…Interestingly, the crosstalk between defense and growth is, at least partially, redox-mediated. The catalase mutant cat2 , which is under constitutive oxidative stress, exhibits dwarfism but has increased resistance against biotrophic pathogens [74–76]. It was found that SA directly binds to plant catalases to inhibit their activity [77,78].…”

“…It was found that SA directly binds to plant catalases to inhibit their activity [77,78]. In A. thaliana , the inhibition of CAT2 activity by SA leads to an increase in H 2 O 2 and subsequent sulfenylation (oxidation of a thiol -SH into sulfenic acid -SOH) of tryptophan synthetase β subunit 1 (TSB1) [76]. Reduced levels of tryptophan, the auxin precursor, cause reduced growth, but stronger immunity.…”

“…Furthermore, because ROS/RNS are required for defense against both biotrophs [27,42,48,50] and necrotrophs/herbivores [45,59], they could also play a significant role in limiting the SA-JA antagonism, which is often exploited by attackers [69,70]. For example, the cat2 mutation increases defense against biotrophs but decreases resistance to necrotrophs by suppressing JA biosynthesis [76]. In contrast, plants without apoplastic peroxidase activity are unable to mount efficient defense against both types of pathogens [45], implying that the source of ROS/RNS also affects how the plants balance SA- and JA-dependent defenses.…”

Peroxisome Function, Biogenesis, and Dynamics in Plants

“…For example, CAT3 and ACX4 activity and transcripts are both elevated by carbon-starvation (Contento and Bassham, 2010). Moreover, cat2 mutants display decreased ACX activity Yuan et al, 2017), and overexpressing ACX3 rescues cat2 seedling growth defects . The finding that ACX activity is limiting for cat2 growth implies that ACX enzymes suffer damage when catalase is dysfunctional.…”