RESUMEN
Lytic polysaccharide monooxygenases (LPMOs) are copper-dependent enzymes that oxidatively cleave recalcitrant polysaccharides such as cellulose. Several studies have reported LPMO action in synergy with other carbohydrate-active enzymes (CAZymes) for the degradation of lignocellulosic biomass but direct LPMO action at the plant tissue level remains challenging to investigate. Here, we have developed a MALDI-MS imaging workflow to detect oxidised oligosaccharides released by a cellulose-active LPMO at cellular level on maize tissues. Using this workflow, we imaged LPMO action and gained insight into the spatial variation and relative abundance of oxidised and non-oxidised oligosaccharides. We reveal a targeted action of the LPMO related to the composition and organisation of plant cell walls.
Asunto(s)
Oxigenasas de Función Mixta , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción , Zea mays , Zea mays/química , Oxigenasas de Función Mixta/metabolismo , Oxigenasas de Función Mixta/química , Espectrometría de Masa por Láser de Matriz Asistida de Ionización Desorción/métodos , Celulosa/química , Celulosa/metabolismo , Pared Celular/química , Pared Celular/metabolismo , Oligosacáridos/química , Oligosacáridos/metabolismo , Lignina/química , Lignina/metabolismo , Oxidación-Reducción , Polisacáridos/química , Polisacáridos/metabolismo , Proteínas de Plantas/química , Proteínas de Plantas/metabolismoRESUMEN
The cuticle constitutes the outermost defensive barrier of most land plants. It comprises a polymeric matrix - cutin, surrounded by soluble waxes. Moreover, the cuticle constitutes the first line of defense against pathogen invasion, while also protecting the plant from many abiotic stresses. Aliphatic monomers in cutin have been suggested to act as immune elicitors in plants. This study analyses the potential of cutin oligomers to activate rapid signaling outputs reminiscent of pattern-triggered immunity (PTI) in the model plant Arabidopsis. Cutin oligomeric mixtures led to Ca2+ influx and MAPK activation. Comparable responses were measured for cutin, which was also able to induce a reactive oxygen species (ROS) burst. Furthermore, cutin oligomer treatment resulted in a unique transcriptional reprogramming profile, having many archetypal features of PTI. Targeted spectroscopic and spectrometric analyses of the cutin oligomers suggest that the elicitors compounds consist mostly of two up to three 10,16-dihydroxyhexadecanoic acid monomers linked together through ester bonds. This study demonstrates that cutin breakdown products can act as inducers of early plant immune responses, which underlying mechanisms of perception and potential use in agriculture warrant further investigation.
