Upon fertilization, the ovary increases in size and undergoes a complex developmental process to become a fruit. We show that cytokinins (CKs), which are required to determine ovary size before fertilization, have to be degraded to facilitate fruit growth. The expression of CKX7, which encodes a cytosolic CK-degrading enzyme, is directly positively regulated post-fertilization by the MADS-box transcription factor STK. Similar to stk, two ckx7 mutants possess shorter fruits than wild type. Quantification of CKs reveals that stk and ckx7 mutants have high CK levels, which negatively control cell expansion during fruit development, compromising fruit growth. Overexpression of CKX7 partially complements the stk fruit phenotype, confirming a role for CK degradation in fruit development. Finally, we show that STK is required for the expression of FUL, which is essential for valve elongation. Overall, we provide insights into the link between CKs and molecular pathways that control fruit growth.
- MeSH
- Arabidopsis anatomie a histologie genetika růst a vývoj MeSH
- cytokininy metabolismus MeSH
- cytosol metabolismus MeSH
- down regulace genetika MeSH
- květy metabolismus MeSH
- modely genetické MeSH
- ovoce anatomie a histologie růst a vývoj MeSH
- proteiny domény MADS metabolismus MeSH
- proteiny huseníčku metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- signální transdukce MeSH
- velikost orgánu MeSH
- zeatin metabolismus MeSH
- zelené fluorescenční proteiny metabolismus MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The phytohormone cytokinin is a regulator of numerous processes in plants. In Arabidopsis (Arabidopsis thaliana), the cytokinin signal is perceived by three membrane-located receptors named ARABIDOPSIS HISTIDINE KINASE2 (AHK2), AHK3, and AHK4/CRE1. How the signal is transmitted across the membrane is an entirely unknown process. The three receptors have been shown to operate mostly in a redundant fashion, and very few specific roles have been attributed to single receptors. Using a forward genetic approach, we isolated constitutively active gain-of-function variants of the AHK2 and AHK3 genes, named repressor of cytokinin deficiency2 (rock2) and rock3, respectively. It is hypothesized that the structural changes caused by these mutations in the sensory and adjacent transmembrane domains emulate the structural changes caused by cytokinin binding, resulting in domain motion propagating the signal across the membrane. Detailed analysis of lines carrying rock2 and rock3 alleles revealed how plants respond to locally enhanced cytokinin signaling. Early flowering time, a prolonged reproductive growth phase, and, thereby, increased seed yield suggest that cytokinin regulates various aspects of reproductive growth. In particular, it counteracts the global proliferative arrest, a correlative inhibition of maternal growth by seeds, an as yet unknown activity of the hormone.
- MeSH
- Arabidopsis anatomie a histologie genetika fyziologie MeSH
- časové faktory MeSH
- cytokininy metabolismus farmakologie MeSH
- geneticky modifikované rostliny MeSH
- histidinkinasa genetika MeSH
- květy genetika fyziologie ultrastruktura MeSH
- meristém genetika fyziologie ultrastruktura MeSH
- mikroskopie elektronová rastrovací MeSH
- mutace * MeSH
- polymerázová řetězová reakce s reverzní transkripcí MeSH
- proteiny huseníčku genetika MeSH
- regulace genové exprese u rostlin MeSH
- regulátory růstu rostlin metabolismus farmakologie MeSH
- rozmnožování genetika fyziologie MeSH
- sekvence aminokyselin MeSH
- sekvenční homologie aminokyselin MeSH
- signální transdukce účinky léků genetika MeSH
- Publikační typ
- časopisecké články MeSH
Growth is the best visible sign of plant comfort. If plants are under stress, a difference in growth with control conditions can indicate that something is going wrong (or better). Phytohormones such as auxin, cytokinins, brassinosteroids or giberellins, are important growth regulators and their role in plant growth was extensively studied. On the other hand the role of salicylic acid (SA), a phytohormone commonly connected with plant defense responses, in plant growth is under-rated. However, studies with SA-overaccumulating mutants directly showed an influence of SA on plant growth. Recently we characterized an Arabidopsis SA-overaccumulating mutant impaired in phosphatidylinositol-4-kinases (pi4kIIIβ1β2). This mutant is dwarf. The crossing with mutants impaired in SA signaling revealed that pi4kIIIβ1β2 stunted rosette is due to high SA, while the short root length is not. This brings into evidence that upper and lower parts of the plants, even though they may share common phenotypes, are differently regulated.
- MeSH
- 1-fosfatidylinositol-4-kinasa genetika MeSH
- Arabidopsis anatomie a histologie enzymologie MeSH
- kořeny rostlin anatomie a histologie MeSH
- kyselina salicylová metabolismus MeSH
- listy rostlin anatomie a histologie MeSH
- mutace genetika MeSH
- proteiny huseníčku genetika MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The cortical microtubules, and to some extent also the actin meshwork, play a central role in the shaping of plant cells. Transgenic plants expressing fluorescent protein markers specifically tagging the two main cytoskeletal systems are available, allowing noninvasive in vivo studies. Advanced microscopy techniques, in particular confocal laser scanning microscopy (CLSM) and variable angle epifluorescence microscopy (VAEM), can be nowadays used for imaging the cortical cytoskeleton of living cells with unprecedented spatial and temporal resolution. With the aid of suitable computing techniques, quantitative information can be extracted from microscopic images and video sequences, providing insight into both architecture and dynamics of the cortical cytoskeleton.
Plant organs and tissues consist of many various cell types, often in different phases of their development. Such complex structures do not allow direct studies on behavior of individual cells. In contrast, populations of in vitro-cultured plant cells represent valuable tool for studying processes on a single-cell level, including cell morphogenesis. Here we describe characteristics of well-established model tobacco and Arabidopsis cell lines and provide detailed protocol on their cultivation, characterization, and genetic transformation.
Phospholipids have recently been found to be integral elements of hormone signalling pathways. An Arabidopsis thaliana double mutant in two type III phosphatidylinositol-4-kinases (PI4Ks), pi4kIIIβ1β2, displays a stunted rosette growth. The causal link between PI4K activity and growth is unknown. Using microarray analysis, quantitative reverse transcription polymerase chain reaction (RT-qPCR) and multiple phytohormone analysis by LC-MS we investigated the mechanism responsible for the pi4kIIIβ1β2 phenotype. The pi4kIIIβ1β2 mutant accumulated a high concentration of salicylic acid (SA), constitutively expressed SA marker genes including PR-1, and was more resistant to Pseudomonas syringae. pi4kIIIβ1β2 was crossed with SA signalling mutants eds1 and npr1 and SA biosynthesis mutant sid2 and NahG. The dwarf phenotype of pi4kIIIβ1β2 rosettes was suppressed in all four triple mutants. Whereas eds1 pi4kIIIβ1β2, sid2 pi4kIIIβ1β2 and NahG pi4kIIIβ1β2 had similar amounts of SA as the wild-type (WT), npr1pi4kIIIβ1β2 had more SA than pi4kIIIβ1β2 despite being less dwarfed. This indicates that PI4KIIIβ1 and PI4KIIIβ2 are genetically upstream of EDS1 and need functional SA biosynthesis and perception through NPR1 to express the dwarf phenotype. The slow root growth phenotype of pi4kIIIβ1β2 was not suppressed in any of the triple mutants. The pi4kIIIβ1β2 mutations together cause constitutive activation of SA signalling that is responsible for the dwarf rosette phenotype but not for the short root phenotype.
- MeSH
- 1-fosfatidylinositol-4-kinasa genetika metabolismus MeSH
- Arabidopsis anatomie a histologie enzymologie genetika růst a vývoj MeSH
- down regulace genetika MeSH
- fenotyp MeSH
- genom rostlinný MeSH
- genotyp MeSH
- kinetika MeSH
- kořeny rostlin anatomie a histologie růst a vývoj MeSH
- kyselina salicylová metabolismus MeSH
- listy rostlin genetika růst a vývoj MeSH
- metabolismus lipidů genetika MeSH
- modely genetické MeSH
- mutace genetika MeSH
- nemoci rostlin genetika imunologie mikrobiologie MeSH
- odolnost vůči nemocem genetika imunologie MeSH
- proteiny huseníčku genetika metabolismus MeSH
- Pseudomonas fyziologie MeSH
- reaktivní formy kyslíku metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- signální transdukce MeSH
- upregulace genetika MeSH
- výhonky rostlin růst a vývoj MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
The effect of recalcitrant soil and water pollutant 2,4,6-trinitrotoluen (TNT) on gene expression in Arabidopsis thaliana rosettes and roots was studied separately for the first time using microarrays. Seven-day exposure to TNT resulted in 170 up- and 122 down-regulated genes in the rosettes and 61 up- and 51 down-regulated genes in the roots (expression difference > 1.5-fold; p[t test] < 0.05). TNT concentration, 5 µg/ml, was selected according to the dose response analysis and study of TNT uptake from liquid media. Although many TNT induced genes fell into ontology groups annotated as response to biotic and abiotic stresses in rosettes and roots, only a small overlap of TNT effects on transcriptome was observed between rosettes and roots. The rosettes exhibited induction of several genes associated with toxin metabolism, such as UDP-glycosyltransferases and ATP-binding cassette (ABC) family transporters. On the other side, no genes known to be involved in TNT transformation were found to be up-regulated in the roots. The genes coding for enzymes involved in the cell wall modifications were abundantly up-regulated in roots. Microarray data indicated that after a relatively long incubation with TNT (7 days), metabolism of this xenobiotic proceeded mainly in aerial parts, while its translocation into cell walls still took place in the roots. Results obtained by microarray hybridization were validated by quantitative real-time reverse-transcription PCR. Nitrate reductase 1, several glycosyltransferases and ABC transporters, sucrose-proton symporter 2, thioredoxin-dependent peroxidase 2, and gamma-glutamyltransferase are discussed for their potential to enhance detoxification and toleration capability of plants to TNT.
- MeSH
- Arabidopsis anatomie a histologie účinky léků metabolismus fyziologie MeSH
- membránové transportní proteiny genetika metabolismus MeSH
- metabolická inaktivace MeSH
- mikročipová analýza MeSH
- molekulární struktura MeSH
- proteiny huseníčku genetika metabolismus MeSH
- regulace genové exprese u rostlin MeSH
- stanovení celkové genové exprese MeSH
- transferasy genetika metabolismus MeSH
- trinitrotoluen farmakokinetika farmakologie MeSH
- výbušné látky farmakokinetika farmakologie MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
