Plastid-encoded RNA polymerase (PEP) forms a multisubunit complex in operating chloroplasts, where PEP subunits and a sigma factor are tightly associated with 12 additional nuclear-encoded proteins. Mutants with disrupted genes encoding PEP-associated proteins (PAPs) provide unique tools for deciphering mutual relationships among phytohormones. A block of chloroplast biogenesis in Arabidopsis pap mutants specifying highly altered metabolism in white tissues induced dramatic fluctuations in the content of major phytohormones and their metabolic genes, whereas hormone signaling circuits mostly remained functional. Reprogramming of the expression of biosynthetic and metabolic genes contributed to a greatly increased content of salicylic acid (SA) and a concomitant decrease in 1-aminocyclopropane-1-carboxylic acid (ACC) and oxophytodienoic acid (OPDA), precursors of ethylene and jasmonic acid, respectively, in parallel to reduced levels of abscisic acid (ABA). The lack of differences in the free levels of indole-3-acetic acid (IAA) between the pap mutants and wild-type plants was accompanied by fluctuations in the contents of IAA precursors and conjugated forms as well as multilayered changes in the expression of IAA metabolic genes. Along with cytokinin (CK) overproduction, all of these compensatory changes aim to balance plant growth and defense systems to ensure viability under highly modulated conditions.
- Klíčová slova
- Arabidopsis thaliana, PEP-associated proteins, gene expression, mutants, phytohormones,
- MeSH
- Arabidopsis * genetika metabolismus MeSH
- chloroplasty metabolismus MeSH
- plastidy genetika MeSH
- proteiny huseníčku * genetika metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- regulátory růstu rostlin metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- proteiny huseníčku * MeSH
- regulátory růstu rostlin MeSH
Cytokinins (CKs) are known to regulate the biogenesis of chloroplasts under changing environmental conditions and at different stages of plant ontogenesis. However, the underlying mechanisms are still poorly understood. Apparently, the mechanisms can be duplicated in several ways, including the influence of nuclear genes that determine the expression of plastome through the two-component CK regulatory circuit. In this study, we evaluated the role of cytokinins and CK signaling pathway on the expression of nuclear genes for plastid RNA polymerase-associated proteins (PAPs). Cytokinin induced the expression of all twelve Arabidopsis thalianaPAP genes irrespective of their functions via canonical CK signaling pathway but this regulation might be indirect taking into consideration their different functions and versatile structure of promoter regions. The disruption of PAP genes contributed to the abolishment of positive CK effect on the accumulation of the chloroplast gene transcripts and transcripts of the nuclear genes for plastid transcription machinery as can be judged from the analysis of pap1 and pap6 mutants. However, the CK regulatory circuit in the mutants remained practically unperturbed. Knock-out of PAP genes resulted in cytokinin overproduction as a consequence of the strong up-regulation of the genes for CK synthesis.
- Klíčová slova
- Arabidopsis thaliana, PEP-associated proteins, chloroplast biogenesis, cytokinin, plastid transcription machinery,
- MeSH
- Arabidopsis účinky léků genetika MeSH
- buněčné jádro účinky léků genetika MeSH
- chloroplasty účinky léků genetika MeSH
- cytokininy farmakologie MeSH
- fotosyntéza účinky léků MeSH
- genetická transkripce účinky léků MeSH
- geny chloroplastů * MeSH
- messenger RNA genetika metabolismus MeSH
- mutace genetika MeSH
- regulace genové exprese u rostlin účinky léků MeSH
- signální transdukce účinky léků MeSH
- zeatin farmakologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- cytokininy MeSH
- messenger RNA MeSH
- zeatin MeSH
