Starch degradation, abscisic acid and vesicular trafficking are important elements in callose priming by indole‐3‐carboxylic acid in response to Plectosphaerella cucumerina infection

Abstract

A fast callose accumulation has been shown to mediate defence priming in certain plant-pathogen interactions, but the events upstream of callose assembly following chemical priming are poorly understood, mainly because those steps comprise sugar transfer to the infection site. β-Amino butyric acid (BABA)-induced resistance in Arabidopsis against Plectosphaerella cucumerina is known to be mediated by callose priming. Indole-3-carboxylic acid (ICOOH, also known as I3CA) mediates BABA-induced resistance in Arabidopsis against P. cucumerina. This indolic compound is found in a common fingerprint of primed metabolites following treatments with various priming stimuli. In the present study, we show that I3CA induces resistance in Arabidopsis against P. cucumerina and primes enhancement of callose accumulation. I3CA treatment increased abscisic acid (ABA) levels before infection with P. cucumerina. An intact ABA synthesis pathway is needed to activate a starch amylase (BAM1) to trigger augmented callose deposition against P. cucumerina during I3CA-IR. To verify the relevance of the BAM1 amylase in I3CA-IR, knockdown mutants and overexpressors of the BAM1 gene were tested. The mutant bam1 was impaired to express I3CA-IR, but complemented 35S::BAM1-YFP lines in the background of bam1 restored an intact I3CA-IR and callose priming. Therefore, a more active starch metabolism is a committed step for I3CA-IR, inducing callose priming in adult plants. Additionally, I3CA treatments induced expression of the ubiquitin ligase ATL31 and syntaxin SYP131, suggesting that vesicular trafficking is relevant for callose priming. As a final element in the callose priming, an intact Powdery Mildew resistant4 (PMR4) gene is also essential to fully express I3CA-IR.

γ‐Aminobutyric acid and related amino acids in plant immune responses: Emerging mechanisms of action

“…Furthermore, BABA priming affects the methylome of plants, resulting in a transcriptional memory of the event which can affect following generations (Kuźnicki et al, ). Recent studies showed how BABA perception reshapes the primary metabolism of plant cells by boosting the TCA cycle and mobilizing starch reservoirs towards callose synthesis and deposition at the infection sites (Gamir et al, ; Pastor, Balmer, Gamir, Flors, & Mauch‐Mani, ; Yao, Zhong, Wang, Yan, & Wu, ).…”

BABA application improves soybean resistance to aphid through activation of phenylpropanoid metabolism and callose deposition

“…Defense response induced by BABA was also observed in the expression of callose synthase genes. Callose accumulation was also reported in Plectosphaerella cucumerina infection, and significantly increased with indole‐3‐carboxylic acid priming …”

“…19,20,[22][23][24] Similar pathways will be stimulated by different priming stimuli/biotic stress. 57 In this study, both BABA and SBA induced the genes involved in the isoflavone phenylpropanoid pathway. Most genes were significantly induced with the combination of BABA and SBA treatment, which were consistent with the increase of isoflavone amount.…”

“…Although isoflavones are the precursors of some major phytoalexins, they have a direct inhibitory effect on some insects . Similar pathways will be stimulated by different priming stimuli/biotic stress . In this study, both BABA and SBA induced the genes involved in the isoflavone phenylpropanoid pathway.…”

“…Callose accumulation was also reported in Plectosphaerella cucumerina infection, and significantly increased with indole-3-carboxylic acid priming. 57 In this study, plant defense response to SBA induced by BABA was effective in the non-caged and caged tests. Furthermore, the in vitro assay using detached leaves with BABA pre-treatment also supported this finding.…”