The rendez-vous of mobile sieve-element and abundant companion-cell proteins

Unveiling the diversity of gut microbes in green lacewings (Chrysopidae: Neuroptera) and their role as protagonist in nutrition

Green lacewings (Chrysopidae; Neuroptera) plays a crucial role as predators against insect pests in diverse cropping systems. Larval chrysopids are predatory on mealybugs, aphids, scales, whiteflies, mites and eggs of many arthropods. Adults are palynoglycophagous and feed on nectar, pollen, and honeydew secreted by aphids. Many insects cannot synthesize necessary vitamins and amino acids on their own and depend on gut microbes. Microbes associated with chrysopid gut help them with balanced nutrition and ecological fitness to withstand extreme stresses, especially adult gut microbiota, which constitutes an indispensable part of nutrients in addition to reproduction. Except for yeast, microbes such as bacteria in the chrysopid larval and adult gut have not been extensively studied. This review aims to seek a comprehensive overview of the gut microbes present in the chrysopids and their role in improving the fitness of chrysopids through adequate nutrition. This will pave the way for further research on understanding the microbe-mediated metabolic activities, their role in toxin production, and the development of probiotic feed from the novel gut microbiota for improving the productivity of laboratory-reared chrysopids used in augmentative biological control of major pests in agricultural ecosystems.

Stationary sieve element proteins

Vascular plants use the phloem to move sugars and other molecules from source leaves to sink organs such as roots and fruits. Within the phloem, enucleate sieve elements provide the low-resistance pipe system that enable bulk flow of sap. In this review, we provide an overview of the highly specific protein machinery that localize to mature sieve elements without entering the phloem translocation stream. Generally, the proteins either maintain the flow, protect the sieve element against pathogens or transmit system wide signals. A notable exception is found in poppy, where part of the opium biosynthesis is compartmentalized in sieve elements. Biosynthesis of sieve element proteins happens either continuously in companion cell or transiently in immature sieve elements before nuclear disintegration. The latter population is translated during differentiation and stays functional without turnover during the entire lifespan of sieve elements. We discuss how protein longevity imposes some interesting restrictions on plants, especially in arborescent monocots with long living sieve elements.

Phloem Exudate Protein Profiles during Drought and Recovery Reveal Abiotic Stress Responses in Tomato Vasculature

Drought is the leading cause of agricultural yield loss among all abiotic stresses, and the link between water deficit and phloem protein contents is relatively unexplored. Here we collected phloem exudates from Solanum lycopersicum leaves during periods of drought stress and recovery. Our analysis identified 2558 proteins, the most abundant of which were previously localized to the phloem. Independent of drought, enrichment analysis of the total phloem exudate protein profiles from all samples suggests that the protein content of phloem sap is complex, and includes proteins that function in chaperone systems, branched-chain amino acid synthesis, trehalose metabolism, and RNA silencing. We observed 169 proteins whose abundance changed significantly within the phloem sap, either during drought or recovery. Proteins that became significantly more abundant during drought include members of lipid metabolism, chaperone-mediated protein folding, carboxylic acid metabolism, abscisic acid signaling, cytokinin biosynthesis, and amino acid metabolism. Conversely, proteins involved in lipid signaling, sphingolipid metabolism, cell wall organization, carbohydrate metabolism, and a mitogen-activated protein kinase are decreased during drought. Our experiment has achieved an in-depth profiling of phloem sap protein contents during drought stress and recovery that supports previous findings and provides new evidence that multiple biological processes are involved in drought adaptation.