Pathogen and drought stress affect cell wall and phytohormone signaling to shape host responses in a sorghum COMT bmr12 mutant

Abstract

Background As effects of global climate change intensify, the interaction of biotic and abiotic stresses increasingly threatens current agricultural practices. The secondary cell wall is a vanguard of resistance to these stresses. Fusarium thapsinum (Fusarium stalk rot) and Macrophomina phaseolina (charcoal rot) cause internal damage to the stalks of the drought tolerant C4 grass, sorghum (Sorghum bicolor (L.) Moench), resulting in reduced transpiration, reduced photosynthesis, and increased lodging, severely reducing yields. Drought can magnify these losses. Two null alleles in monolignol biosynthesis of sorghum (brown midrib 6-ref, bmr6-ref; cinnamyl alcohol dehydrogenase, CAD; and bmr12-ref; caffeic acid O-methyltransferase, COMT) were used to investigate the interaction of water limitation with F. thapsinum or M. phaseolina infection. Results The bmr12 plants inoculated with either of these pathogens had increased levels of salicylic acid (SA) and jasmonic acid (JA) across both watering conditions and significantly reduced lesion sizes under water limitation compared to adequate watering, which suggested that drought may prime induction of pathogen resistance. RNA-Seq analysis revealed coexpressed genes associated with pathogen infection. The defense response included phytohormone signal transduction pathways, primary and secondary cell wall biosynthetic genes, and genes encoding components of the spliceosome and proteasome. Conclusion Alterations in the composition of the secondary cell wall affect immunity by influencing phenolic composition and phytohormone signaling, leading to the action of defense pathways. Some of these pathways appear to be activated or enhanced by drought. Secondary metabolite biosynthesis and modification in SA and JA signal transduction may be involved in priming a stronger defense response in water-limited bmr12 plants.

Metabolic and Transcriptional Stress Memory in Sorbus pohuashanensis Suspension Cells Induced by Yeast Extract

“…The plant cell wall, a formidable and dynamic barrier, acts as the hub of stress surveillance and response [ 28 ]. Cellulose is the major component of the plant cell wall, and its degradation and/or the inhibition of its biosynthesis can be generally triggered by microbial attack, leading to the degradation of the cell wall [ 29 , 30 ].…”

Singlet oxygen makes plant epidermis thicker with less stomata

“…Plant cell walls are the rst physical barrier against pathogenic invasion. Under biotic stresses, plants thicken their cell walls to strengthen them and restrain pathogenic infections [33][34][35] . And cell wall thickening would enhance plant's tolerance to drought 35,36 , salinity / osmotic stress 37,38 , mental stress 39,40 and especially waterlogging stress 36,41,42 by improving mechanical strength and facilitating water transport.…”

“…Under biotic stresses, plants thicken their cell walls to strengthen them and restrain pathogenic infections [33][34][35] . And cell wall thickening would enhance plant's tolerance to drought 35,36 , salinity / osmotic stress 37,38 , mental stress 39,40 and especially waterlogging stress 36,41,42 by improving mechanical strength and facilitating water transport. Tailoring the content and structure of plant cell walls could modulate growth, abiotic / biotic stress resistance, biomass yield and other important agronomic traits 42 .…”

A generic part of specific combined responses to biotic and abiotic stresses in crops: Overcoming multifaceted challenges towards new opportunities

“…One of the major difficulties in evaluating CS responses is the choice of relevant variables which can specifically characterize the concurrent action of the stressors. Assessed at different scales, ranging from the anatomical (Wiese et al, 2004), cellular (Khasin et al, 2021), physiological (Chekali et al, 2011), metabolic (Cohen et al, 2017;Christensen et al, 2021), genetic (Choi et al, 2013;Vemanna et al, 2019) to the epigenetic level (Rodriguez-Algaba et al, 2019), they usually consist of variables that perfectly characterize single stress conditions but neglect specific crosseffects of stress combinations. Variables shared between stresses constituting the combination, such as phytohormone balance or oxidative markers, are suggested (Pandey et al, 2017;Anwar et al, 2021) but bona fide parameters still have to be compared between individual, combined or sequential stresses.…”