Epsilon Archive for Student Projects

Abstract

System based models of plants rely on descriptions and assigned functions of genes, and currently 50% of the genes in Arabidopsis thaliana has either no assigned function or a function based on homology only. Mitogen activated protein kinases (MAPK's) are key players in cell signalling and are conserved among eukaryotes, though their targets are highly diverse. A recent study has described a small Arabidopsis protein (80), without homology to any described protein, as a phosphorylation target of the MAPK's MPK3/6. Further work established α-glucan phosphorylase (PHS) as interacting with 80 and described a delayed senescence phenotype for 80 knock-out plants. This work has examined the effect of flagellin and sucrose on the stability of the 80 protein in seedling culture. In whole plants the effect of 80 on glucose, sucrose and the glucose residue content of the soluble heteroglycan (SHG) pool, as well as 80's stability during senescence has been investigated. 80 was found to be degraded under induced leaf senescence, in a way similar to that of induced darkness in whole plant systems. At day-time leaves from 80knock-out plants exhibited an increase in sucrose and no changes in glucose content. At night-time 80knock-out plants exhibited an increased sucrose:glucose ratio.

80knock-out leaves did not exhibit significant changes in sucrose and glucose content during senescence. In seedlings, 80 was found to be stabilised by sucrose and flagellin, though the sucrose dependent stabilisation was partly inhibited by flagellin.

Systembaserade modeller för växter baseras på dokumenterade beskrivningar av olika geners funktioner, och 50 % av generna i Arabidopsis thaliana har antingen ingen känd funktion eller enbart en presumtiv funktion baserad på homologi baserade med kända proteiner. Mitogen aktiverade protein kinaser (MAPK's) är viktiga delar av ellsignalleringen och ser väldigt lika ut mellan eukaryoter. De proteiner som fosforyleras av MAP kinaserna är däremot väldigt skiftande.

Nyligen beskrevs a litet protein utan homologi till något känt protein, 80, som ett MPK3/6 fosforyleringsmål. Vidare studier har identifierat ett protein som interagerar med 80, ett α-glukan fosforylas (PHS). En försenad senescens och har också hittats hos blad av 80knock-outplantor som
saknar en fungerande 80 gen (80 knockout). Det här arbetet har studerat hur 80 regleras av flagellin och sackaros i sterilkultur. I hela plantor har 80's effekt på glukos, sackaros och den lösliga heteroglukan (SHG) bundna glukospoolen studerats, liksom dess stabilitet under senescens. 80 degraderades vid inducerad senescens på samma sätt som under inducerat mörker i hela plantor. Under dagen hade blad från 80knockout plantor högre sackaros innehåll men oförändrade glukos nivåer, jämfört med vildtyps plantor. Under natten hade 80knockout en signifikant högre sackaros:glukos ratio.

80 hade ingen signifikant inverkan på sockerhalten under senescens. I sterilkultur stabiliserades 80 av sackaros och flagellin, men den sackaros beroende stabiliseringen delvis motverkades av flagellin.