Abstract
Microbial volatiles promote accumulation of exceptionally high levels of starch in leaves. This phenomenon (designated as MIVOISAP) is inhibited by cycloheximide and cordycepin. Transcriptomic analyses revealed that Arabidopsis MIVOISAP is accompanied by drastic transcriptome reprogramming. Using different Arabidopsis mutants we investigated the impact in MIVOISAP of down-regulation of starch genes and of genes involved in the main signaling pathways. These analyses revealed that starch content increase in microbial volatiles-treated hy1 and hy2 photoreceptor mutants, and in mutants impaired in starch synthases class III (SS3) and IV (SS4), jasmonic acid (JA) sensing, and plastidial NADP-thioredoxin reductase C (NTRC) was low, whereas starch content increase was highest in bam1, isa3 and phs1 mutants impaired in starch breakdown enzymes. The overall data showed that MIVOISAP involves a photocontrolled, transcriptionally and post-transcriptionally regulated network wherein JA, SS3, SS4 and NTRC-mediated changes in redox status of plastidial enzyme(s) play important roles. We also provide evidence that microbial volatiles activate starch degradation during starch over-accumulation
