PpORS, an ancient type III polyketide synthase, is required for integrity of leaf cuticle and resistance to dehydration in the moss, Physcomitrella patens

Abstract

PpORS knockout mutants produced abnormal leaves with increased dye permeability and were more susceptible to dehydration, consistent with PpORS products being constituents of a cuticular structure in the moss. Type III polyketide synthases (PKSs) have co-evolved with terrestrial plants such that each taxon can generate a characteristic collection of polyketides, fine-tuned to its needs. 2'-Oxoalkylresorcinol synthase from Physcomitrella patens (PpORS) is basal to all plant type III PKSs in phylogenetic trees and may closely resemble their most recent common ancestor. To gain insight into the roles that ancestral plant type III PKSs might have played during early land plant evolution, we constructed and phenotypically characterized targeted knockouts of PpORS. Ors gametophores, unless submerged in water while they were developing, displayed various leaf malformations that included grossly misshapen leaves, missing or abnormal midribs, multicellular protuberances and localized necrosis. Ors leaves, particularly abnormal ones, showed increased permeability to the hydrophilic dye, toluidine blue. Ors gametophores lost water faster and were more susceptible to dehydration than those of the control strain. Our findings are consistent with ors leaves possessing a partially defective cuticle and implicate PpORS in synthesis of the intact cuticle. PpORS orthologs are present in a few moss species but have not been found in other plants. However, conceivably an ancestral ORS in early land plants may have contributed to their protection from dehydration.

Cinnamomum zeylanicum bark essential oil induces cell wall remodelling and spindle defects in Candida albicans

“…Cells were examined using an Eclipse 80i microscope (Nikon) at 40× magnification. A minimum of 100 cells in consecutive visual fields were examined and the percentage of stained cells were calculated using the Nikon SPOT software [ 44 ].…”

The Origin and Evolution of Plant Flavonoid Metabolism

“…Phylogenetic analyses show that the ARAS/ARS and ASCL families are classified into distinct groups (Figure 3) (Shimizu et al, 2017). Bacteria, fungi, and mosses also have genes encoding type III PKSs that produce these long-chain fatty acyl containing-polyketides (Colpitts et al, 2011; Shimizu et al, 2017; Li et al, 2018). Therefore, these type III PKSs are involved in lipid metabolism across three kingdoms of living organisms.…”

Membrane Lipids, Waxes and Oxylipins in the Moss Model Organism Physcomitrella patens

“…1998, Ariizumi and Toriyama 2011). Despite the fact that sporopollenin was not found in P. patens , an enzyme involved in its biosynthesis (the type III polyketide synthase—PpORS) was recently characterized in this organism (Li et�al. 2018).…”

“…Mutants of PpORS showed malformed phyllids (leaf-like structures) and could not recover after desiccation. It was suggested that mutants of PpORS have a compromised or defective cuticle and it may therefore be that the sporopollenin synthesis pathway also evolved from the same ancestor as the cuticle pathway (Li et�al. 2018).…”

“…There is evidence suggesting the existence of a hydrophobic layer in first land plants being a common ancestor of the formation of cutin, suberin, lignin and also sporopollenin (Renault et�al. 2017, Li et�al. 2018).…”