Sweet immunity : inulin boosts resistance of lettuce (Lactuca sativa) against grey mold (Botrytis cinerea) in an ethylene-dependent manner

The concept of Sweet Immunity postulates that sugar metabolism and signaling influence plant immune networks. In this study, we tested the potential of commercially available inulin-type fructans to limit disease symptoms caused by Botrytis cinerea in lettuce. Spraying mature lettuce leaves, with inulin-type fructans derived from burdock or chicory was as effective in reducing grey mold disease symptoms caused by Botrytis cinerea as spraying with oligogalacturonides (OGs). OGs are well-known defense elicitors in several plant species. Spraying with inulin and OGs induced accumulation of hydrogen peroxide and levels further increased upon pathogen infection. Inulin and OGs were no longer able to limit Botrytis infection when plants were treated with the ethylene signaling inhibitor 1-methylcyclopropene (1-MCP), indicating that a functional ethylene signaling pathway is needed for the enhanced defense response. Soluble sugars accumulated in leaves primed with OGs, while 1-MCP treatment had an overall negative effect on the sucrose pool. Accumulation of -aminobutyric acid (GABA), a stress-associated non-proteinogenic amino acid and possible signaling compound, was observed in inulin-treated samples after infection and negatively affected by the 1-MCP treatment. We have demonstrated for the first time that commercially available inulin-type fructans and OGs can improve the defensive capacity of lettuce, an economically important species. We discuss our results in the context of a possible recognition of fructans as Damage or Microbe Associated Molecular Patterns

Linking Autophagy to Abiotic and Biotic Stress Responses

Autophagy is a process in which cellular components are delivered to lytic vacuoles to be recycled and has been demonstrated to promote abiotic/biotic stress tolerance. Here, we review how the responses triggered by stress conditions can affect autophagy and its signaling pathways. Besides the role of SNF-related kinase 1 (SnRK1) and TOR kinases in the regulation of autophagy, abscisic acid (ABA) and its signaling kinase SnRK2 have emerged as key players in the induction of autophagy under stress conditions. Furthermore, an interplay between reactive oxygen species (ROS) and autophagy is observed, ROS being able to induce autophagy and autophagy able to reduce ROS production. We also highlight the importance of osmotic adjustment for the successful performance of autophagy and discuss the potential role of GABA in plant survival and ethylene (ET)-induced autophagy

Linking Autophagy to Abiotic and Biotic Stress Responses

Autophagy is a process in which cellular components are delivered to lytic vacuoles to be recycled and has been demonstrated to promote abiotic/biotic stress tolerance. Here, we review how the responses triggered by stress conditions can affect autophagy and its signaling pathways. Besides the role of SNF-related kinase 1 (SnRK1) and TOR kinases in the regulation of autophagy, abscisic acid (ABA) and its signaling kinase SnRK2 have emerged as key players in the induction of autophagy under stress conditions. Furthermore, an interplay between reactive oxygen species (ROS) and autophagy is observed, ROS being able to induce autophagy and autophagy able to reduce ROS production. We also highlight the importance of osmotic adjustment for the successful performance of autophagy and discuss the potential role of GABA in plant survival and ethylene (ET)-induced autophagy.This is a manuscript of an article is published as Signorelli, Santiago, Łukasz Paweł Tarkowski, Wim Van den Ende, and Diane C. Bassham. "Linking Autophagy to Abiotic and Biotic Stress Responses." Trends in plant science (2019). doi: 10.1016/j.tplants.2019.02.001. Posted with permission.</p

Crystal structure of Arabidopsis thaliana neutral invertase 2

The metabolism of sucrose is of crucial importance for life on Earth. In plants, enzymes called invertases split sucrose into glucose and fructose, contributing to the regulation of metabolic fluxes. Invertases differ in their localization and pH optimum. Acidic invertases present in plant cell walls and vacuoles belong to glycoside hydrolase family 32 (GH32) and have an all-β structure. In contrast, neutral invertases are located in the cytosol and organelles such as chloroplasts and mitochondria. These poorly understood enzymes are classified into a separate GH100 family. Recent crystal structures of the closely related neutral invertases InvA and InvB from the cyanobacterium Anabaena revealed a predominantly α-helical fold with unique features compared with other sucrose-metabolizing enzymes. Here, a neutral invertase (AtNIN2) from the model plant Arabidopsis thaliana was heterologously expressed, purified and crystallized. As a result, the first neutral invertase structure from a higher plant has been obtained at 3.4 Å resolution. The hexameric AtNIN2 structure is highly similar to that of InvA, pointing to high evolutionary conservation of neutral invertases.status: publishe