Photosynthesis, photorespiration, and light signalling in defence responses

Abstract

Visible light is the basic energetic driver of plant biomass production through photosynthesis. The constantly fluctuating availability of light and other environmental factors means that the photosynthetic apparatus must be able to operate in a dynamic fashion appropriate to the prevailing conditions. Dynamic regulation is achieved through an array of homeostatic control mechanisms that both respond to and influence cellular energy and reductant status. In addition, light availability and quality are continuously monitored by plants through photoreceptors. Outside the laboratory growth room, it is within the context of complex changes in energy and signalling status that plants must regulate pathways to deal with biotic challenges, and this can be influenced by changes in the highly energetic photosynthetic pathways and in the turnover of the photosynthetic machinery. Because of this, defence responses are neither simple nor easily predictable, but rather conditioned by the nutritional and signalling status of the plant cell. This review discusses recent data and emerging concepts of how recognized defence pathways interact with and are influenced by light-dependent processes. Particular emphasis is placed on the potential roles of the chloroplast, photorespiration, and photoreceptor-associated pathways in regulating the outcome of interactions between plants and pathogenic organisms.

Plant Responses to Salt Stress: Adaptive Mechanisms

“…In contrast, in leaf or root peroxisomes from salt-treated plants, no important changes in O2 .-or H2O2 concentration have been reported [25,26,190], although lipid peroxidation levels have increased in some cases. In pea leaf peroxisomes, H2O2 concentrations were even statistically lower in the presence of NaCl than in control plants, in spite of the inhibition of catalase (an H2O2-scavenger enzyme) and an increase in the H2O2-producing enzyme glycollate oxidase [189].…”

“…In addition, the photorespiratory pathway serves to convert phosphoglycolate (2PG) to 3-phosphoglycerate (3PGA), which can be metabolised to either regenerate RuBP or to make complex sugars and other carbon-based organic metabolites [188]. These effects can be even more important considering that different stress conditions can increase photorespiratory rates [189]. Drought and salinity, for example, trigger a decrease in stomatal conductance, thus decreasing the CO2:O2 ratio and increasing photorespiration [189].…”

“…These effects can be even more important considering that different stress conditions can increase photorespiratory rates [189]. Drought and salinity, for example, trigger a decrease in stomatal conductance, thus decreasing the CO2:O2 ratio and increasing photorespiration [189]. Under salinity conditions, the photorespiratory pathway can prevent photo-oxidative damage by continuously recycling CO2 for the chloroplast from the decarboxylation of glycine in the mitochondria.…”

Trichoderma gamsii affected herbivore feeding behaviour on Arabidopsis thaliana by modifying the leaf metabolome and phytohormones

“…Another possibility is that T. gamsii F18 may be able to intensify the plant's immune reactions by reducing the sugar pools in favour of defence. Plant defence responses require the primary metabolites to support cellular energy and impose a fitness cost (Heil and Baldwin, 2002; Kangasjarvi et al ., 2012). …”

Perturbation of Maize Phenylpropanoid Metabolism by an AvrE Family Type III Effector fromPantoea stewartii

“…WtsE suppressed the expression of numerous genes involved in photosynthesis, a common response in plant-microbe interactions. The perturbation of photosynthetic pathways can have profound effects on plant responses, but these are typically context specific, depending on both host and pathogen, and difficult to predict (Kangasjȁrvi et al, 2012). Conversely, WtsE induced the expression of genes in the shikimate and phenylpropanoid pathways.…”