Emerging trade‐offs – impact of photoprotectants (PsbS, xanthophylls, and vitamin E) on oxylipins as regulators of development and defense

Abstract

SummaryThis review summarizes evidence for a mechanistic link between plant photoprotection and the synthesis of oxylipin hormones as regulators of development and defense. Knockout mutants of Arabidopsis, deficient in various key components of the chloroplast photoprotection system, consistently produced greater concentrations of the hormone jasmonic acid or its precursor 12-oxo-phytodienoic acid (OPDA), both members of the oxylipin messenger family. Characterized plants include several mutants deficient in PsbS (an intrinsic chlorophyll-binding protein of photosystem II) or pigments (zeaxanthin and/or lutein) required for photoprotective thermal dissipation of excess excitation energy in the chloroplast and a mutant deficient in reactive oxygen detoxification via the antioxidant vitamin E (tocopherol). Evidence is also presented that certain plant defenses against herbivores or pathogens are elevated for these mutants. This evidence furthermore indicates that wild-type Arabidopsis plants possess less than maximal defenses against herbivores or pathogens, and suggest that plant lines with superior defenses against abiotic stress may have lower biotic defenses. The implications of this apparent trade-off between abiotic and biotic plant defenses for plant ecology as well as for plant breeding/engineering are explored, and the need for research further addressing this important issue is highlighted.

Adaptation of the Long-Lived Monocarpic Perennial, Saxifraga longifolia to High Altitude

“…(Davies, 2010). It is also likely that reduced jasmonic acid levels result from a trade-off between activation of different defense pathways in plants (photoprotection versus potential chemical defense to necrotrophs through jasmonates), so that enhanced vitamin E accumulation at the highest altitude may negatively influence the biosynthesis of jasmonates, which is in agreement with previous studies (Demmig-Adams et al, 2013, 2014Simancas and Munné-Bosch, 2015). Enhanced jasmonic acid accumulation in the intermediate population may reflect activation of acclimation responses, but also increased cell death, as shown in other studies (Shumbe et al, 2016).…”

Heteroblastic Development of Transfer Cells Is Controlled by the microRNA miR156/SPL Module

“…PP is often the primary target of phloem-feeding pathogens (Ding et al, 1998;Zhou et al, 2002), hence the bulky and highly localized deposition of wall ingrowths in PP TCs adjacent to SEs may act as a physical barrier to impede systemic pathogen spread (Amiard et al, 2007). This possibility is supported by the observations that the extent of wall ingrowth deposition in PP TCs can be triggered by the defense hormone jasmonic acid (JA; Amiard et al, 2007;Demmig-Adams et al, 2013), and that aphids, the major group of phloem-feeding insects, activate JA-mediated defense pathways (Louis et al, 2012) and stimulate cell wall modifications (Divol et al, 2005). In contrast to this result, wall ingrowth deposition in CC TCs in pea (Pisum sativum) leaf veins was not enhanced by exogenous methyl jasmonate, consistent with these wall ingrowths serving a primary role in enhancing phloem loading capacity (Wimmers and Turgeon, 1991;Amiard et al, 2007).…”

Multiple feedbacks between chloroplast and whole plant in the context of plant adaptation and acclimation to the environment

“…Chloroplast antioxidant defences (figure 1) de-excite, and thereby detoxify, both singlet oxygen and superoxide, but highly excessive light levels presumably allow remaining ROS to trigger multiple redox-associated signalling pathways. For selected reviews of various examples of the many different components of the redox-signalling network originating in the chloroplast, see the studies of Munné-Bosch et al We will highlight a selected example of one such signalling pathway, leading to the lipid-peroxidation-derived oxylipin messengers (figure 1), that had previously been shown to be involved in the regulation of the biosynthesis of chloroplast antioxidants and facilitators of thermal dissipation [53][54][55] and are now emerging as themselves being subjected to modulation by some of these same chloroplast antioxidants and facilitators of thermal dissipation [56] (table 1). We are highlighting this specific example among the many redox-signalling networks because of the connections that have been made between this particular signalling pathway and phloem loading/transport.…”

“…The PsbS-deficient npq4 mutant exhibited significantly greater oxylipin levels than wild-type under herbivore attack in the field but not in the absence of herbivores. mutant or treatment resulting effect sources vte mutant (tocopherol-/'vitamin E'-deficient) callose deposition resulting in enhanced wall ingrowths in phloem-loading complexes [57] oxylipin (methyl jasmonate) treatment enhanced wall ingrowths in phloem-loading complexes [58] npq1 lut2 mutants (zeaxanthin-and lutein-deficient) enhanced wall ingrowths in phloem-loading complexes [56] npq4 mutant (PsbS-deficient) enhanced herbivore resistance [59] vte mutant (tocopherol-/'vitamin E'-deficient) enhanced oxylipin levels and enhanced ROS levels [60 -63] npq1 mutant (zeaxanthin-deficient) enhanced oxylipin levels [56] npq4 mutant (PsbS-deficient) enhanced oxylipin levels and enhanced ROS levels [59,64] rstb.royalsocietypublishing.org Phil. Trans.…”