Volatile compounds (VCs) emitted by phylogenetically diverse microorganisms (including plant pathogens and microbes that do not normally interact mutualistically with plants) promote photosynthesis, growth, and the accumulation of high levels of starch in leaves through cytokinin (CK)-regulated processes. In Arabidopsis (Arabidopsis thaliana) plants not exposed to VCs, plastidic phosphoglucose isomerase (pPGI) acts as an important determinant of photosynthesis and growth, likely as a consequence of its involvement in the synthesis of plastidic CKs in roots. Moreover, this enzyme plays an important role in connecting the Calvin-Benson cycle with the starch biosynthetic pathway in leaves. To elucidate the mechanisms involved in the responses of plants to microbial VCs and to investigate the extent of pPGI involvement, we characterized pPGI-null pgi1-2 Arabidopsis plants cultured in the presence or absence of VCs emitted by Alternaria alternata We found that volatile emissions from this fungal phytopathogen promote growth, photosynthesis, and the accumulation of plastidic CKs in pgi1-2 leaves. Notably, the mesophyll cells of pgi1-2 leaves accumulated exceptionally high levels of starch following VC exposure. Proteomic analyses revealed that VCs promote global changes in the expression of proteins involved in photosynthesis, starch metabolism, and growth that can account for the observed responses in pgi1-2 plants. The overall data show that Arabidopsis plants can respond to VCs emitted by phytopathogenic microorganisms by triggering pPGI-independent mechanisms.

• MeSH
• Alternaria chemie   účinky záření   MeSH
• Arabidopsis enzymologie   růst a vývoj   mikrobiologie   fyziologie   MeSH
• buněčná stěna metabolismus   účinky záření   MeSH
• cytokininy metabolismus   MeSH
• fotosyntéza účinky záření   MeSH
• glukosa-6-fosfátisomerasa metabolismus   MeSH
• mezofylové buňky účinky léků   metabolismus   účinky záření   MeSH
• mutace genetika   MeSH
• plastidy účinky léků   enzymologie   MeSH
• proteiny huseníčku metabolismus   MeSH
• proteom metabolismus   MeSH
• škrob metabolismus   MeSH
• světlo MeSH
• těkavé organické sloučeniny farmakologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• cytokininy MeSH
• glukosa-6-fosfátisomerasa MeSH
• proteiny huseníčku MeSH
• proteom MeSH
• škrob MeSH
• těkavé organické sloučeniny MeSH

Phosphoglucose isomerase (PGI) catalyzes the reversible isomerization of glucose-6-phosphate and fructose-6-phosphate. It is involved in glycolysis and in the regeneration of glucose-6-P molecules in the oxidative pentose phosphate pathway (OPPP). In chloroplasts of illuminated mesophyll cells PGI also connects the Calvin-Benson cycle with the starch biosynthetic pathway. In this work we isolated pgi1-3, a mutant totally lacking pPGI activity as a consequence of aberrant intron splicing of the pPGI encoding gene, PGI1. Starch content in pgi1-3 source leaves was ca. 10-15% of that of wild type (WT) leaves, which was similar to that of leaves of pgi1-2, a T-DNA insertion pPGI null mutant. Starch deficiency of pgi1 leaves could be reverted by the introduction of a sex1 null mutation impeding β-amylolytic starch breakdown. Although previous studies showed that starch granules of pgi1-2 leaves are restricted to both bundle sheath cells adjacent to the mesophyll and stomata guard cells, microscopy analyses carried out in this work revealed the presence of starch granules in the chloroplasts of pgi1-2 and pgi1-3 mesophyll cells. RT-PCR analyses showed high expression levels of plastidic and extra-plastidic β-amylase encoding genes in pgi1 leaves, which was accompanied by increased β-amylase activity. Both pgi1-2 and pgi1-3 mutants displayed slow growth and reduced photosynthetic capacity phenotypes even under continuous light conditions. Metabolic analyses revealed that the adenylate energy charge and the NAD(P)H/NAD(P) ratios in pgi1 leaves were lower than those of WT leaves. These analyses also revealed that the content of plastidic 2-C-methyl-D-erythritol 4-phosphate (MEP)-pathway derived cytokinins (CKs) in pgi1 leaves were exceedingly lower than in WT leaves. Noteworthy, exogenous application of CKs largely reverted the low starch content phenotype of pgi1 leaves. The overall data show that pPGI is an important determinant of photosynthesis, energy status, growth and starch accumulation in mesophyll cells likely as a consequence of its involvement in the production of OPPP/glycolysis intermediates necessary for the synthesis of plastidic MEP-pathway derived hormones such as CKs.

• MeSH
• alely MeSH
• Arabidopsis genetika   metabolismus   MeSH
• cukerné fosfáty metabolismus   MeSH
• cytokininy metabolismus   MeSH
• erythritol analogy a deriváty   metabolismus   MeSH
• fenotyp MeSH
• fotosyntéza * MeSH
• genetické lokusy MeSH
• glukosa-6-fosfátisomerasa chemie   genetika   metabolismus   MeSH
• listy rostlin metabolismus   MeSH
• metabolické sítě a dráhy MeSH
• mezofylové buňky metabolismus   MeSH
• mutace MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• škrob metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• 2-C-methylerythritol 4-phosphate MeSH Prohlížeč
• cukerné fosfáty MeSH
• cytokininy MeSH
• erythritol MeSH
• glukosa-6-fosfátisomerasa MeSH
• proteiny huseníčku MeSH
• škrob MeSH