Post-Synthetic Reduction of Pectin Methylesterification Causes Morphological Abnormalities and Alterations to Stress Response in Arabidopsis thaliana

Abstract

Pectin is a critical component of the plant cell wall, supporting wall biomechanics and contributing to cell wall signaling in response to stress. The plant cell carefully regulates pectin methylesterification with endogenous pectin methylesterases (PMEs) and their inhibitors (PMEIs) to promote growth and protect against pathogens. We expressed Aspergillus nidulans pectin methylesterase (AnPME) in Arabidopsis thaliana plants to determine the impacts of methylesterification status on pectin function. Plants expressing AnPME had a roughly 50% reduction in methylester content compared with control plants. AnPME plants displayed a severe dwarf phenotype, including small, bushy rosettes and shorter roots. This phenotype was caused by a reduction in cell elongation. Cell wall composition was altered in AnPME plants, with significantly more arabinose and significantly less galacturonic acid, suggesting that plants actively monitor and compensate for altered pectin content. Cell walls of AnPME plants were more readily degraded by polygalacturonase (PG) alone but were less susceptible to treatment with a mixture of PG and PME. AnPME plants were insensitive to osmotic stress, and their susceptibility to Botrytis cinerea was comparable to wild type plants despite their compromised cell walls. This is likely due to upregulated expression of defense response genes observed in AnPME plants. These results demonstrate the importance of pectin in both normal growth and development, and in response to biotic and abiotic stresses.

Polygalacturonase activity promotes aberrant cell separation in the quasimodo2 mutant of Arabidopsis thaliana

“…(C) DM estimation from AIR of 6-day-old etiolated Col, qua2 , and qua2 esmd1 seedlings (n = 15 total technical replicates of methyl-ester content (nmol / mg) determination from 3 biological samples per genotype and age, divided by the average uronic acid content (nmol / mg) of a given biological sample). (D-I) Contrast-enhanced images of 6-d-old etiolated seedling epidermal cells stained with PI from (D) Col, (E-F) alcohol inducible AtPME5-OE seedlings ( Peaucelle et al, 2008 ) after 3 and 6 d of induction, respectively, and (G-I) fungal PME overexpression lines ( Reem et al, 2020 ) with normal cell adhesion (G, I), or defective cell adhesion (H). (A,C) Error bars represent SE.…”

“…Constitutive overexpression of an Aspergillus nidulans PME in Arabidopsis was recently shown to limit plant growth to varying degrees ( Reem et al, 2020 ). The two most severely stunted AnPME -expressing lines (PME2-1 and PME3-2; Reem et al, 2020 ) occasionally exhibited bulging cells and lesions in 6-d-old etiolated seedlings ( Fig. 4 G-I), but to varying degrees in each seedling.…”

PcGCE is a potent elicitor of defense responses in aspen

“…Thus, the expression of microbial enzymes in plants potentially could trigger DAMP or PAMP signaling and activate defense responses and 4 immunity. Indeed, transgenic plants expressing microbial enzymes frequently exhibit increased immunity against different pathogens (Pogorelko et al, 2013;Klose et al, 2015;Pawar et al, 2016;Reem et al, 2020). Among different microbial enzymes, glucuronoyl esterase (GCE) has a potential for decreasing lignocellulose recalcitrance by hydrolyzing the ester bond between 4-O-methyl-α-D-glucuronic acid and lignin (Spániková and Biely, 2006;Biely et al, 2015;Bååth et al, 2016).…”

“…It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in The copyright holder for this this version posted September 24, 2021. ; https://doi.org/10.1101/2021.09.23.460629 doi: bioRxiv preprint 4 immunity. Indeed, transgenic plants expressing microbial enzymes frequently exhibit increased immunity against different pathogens (Pogorelko et al, 2013;Klose et al, 2015;Pawar et al, 2016;Reem et al, 2020). Among different microbial enzymes, glucuronoyl esterase (GCE) has a potential for decreasing lignocellulose recalcitrance by hydrolyzing the ester bond between 4-O-methyl-α-D-glucuronic acid and lignin (Spániková and Biely, 2006;Biely et al, 2015;Bååth et al, 2016).…”

“…Thus, the expression of microbial enzymes in plants potentially could trigger DAMP or PAMP signaling and activate defense responses and 4 immunity. Indeed, transgenic plants expressing microbial enzymes frequently exhibit increased immunity against different pathogens (Pogorelko et al, 2013;Klose et al, 2015;Pawar et al, 2016;Reem et al, 2020).…”