PubMed · 12357617
The source did not provide an abstract. Follow the original record for more information.
Explore connections, maps & timelines
Munetaka Sugiyama. 2002. [Organogenesis in vitro].. https://pubmed.ncbi.nlm.nih.gov/12357617/
Cite the original work for its findings. Save a collection to share your selection of sources.
KEEP EXPLORING
The transcription factor WIP2/NO TRANSMITTING TRACT (WIP2/NTT) belongs to the WIP zinc finger family. Loss of WIP/NTT function in Arabidopsis thaliana causes alterations in specific tissues in the gynoecium. It also impairs root development, but only when combined with the loss of WIP4 and WIP5 function, due to redundancy. Certain mutant loss-of-function phenotypes can be recovered by cytokinin application, NTT interacts with cytokinin signaling components, and the phenotypes displayed by plants with increased WIP2/NTT expression also suggest a possible interaction with this pathway. Therefore, the objective of this study was to investigate the relationship between WIP2/NTT and the cytokinin pathway. To overcome the issue of genetic redundancy, we used a commonly used inducible system. We found that WIP2/NTT induction alters cytokinin levels and signaling in a tissue-specific manner, as shown by cytokinin content measurements and TCSn::GFP reporter analysis. Transcriptome analyses revealed candidate target genes related to the cytokinin pathway. Yeast one-hybrid and transactivation assays demonstrated direct NTT binding to regulatory regions of the cytokinin genes ISOPENTENYL TRANSFERASE 5 (IPT5), ARABIDOPSIS HISTIDINE PHOSPHOTRANSFER PROTEIN 6 (AHP6), and CYTOKININ OXIDASE/DEHYDROGENASE 7 (CKX7) involved in cytokinin biosynthesis, signaling, and degradation, respectively. Moreover, immunolocalization assays revealed that cytokinin distribution was altered in loss of function mutants and after NTT induction. The results of this work indicate that WIP2/NTT modulates cytokinin homeostasis.
The fact that auxin induces root formation has been known for more than half a century. However, despite the recent progress in this field, neither the molecular processes in which the auxin-responsive genes leading to root formation nor the interactions between phytohormones and other bioactive molecules during the commitment phase of root formation are well understood. Here the effect of biomolecules such as cytokinin, glutathione, and flavonoids, as well as the expression of several transcription factors in in vitro root formation in model legume Medicago truncatula are presented. It was demonstrated that auxin NAA (1-naphthaleneacetic acid) pretreatment for 7 d can irreversibly interrupt somatic embryo formation, whilst both reduced and oxidized forms of glutathione enhance root formation via a mechanism independent of ethylene perception, as determined by analysis of the ethylene-insensitive skl mutant. It was also shown that quercetin and the well-known auxin transport inhibitor NPA (N-1-naphthylphthalamic acid), which has a similar structure to quercetin, and isoflavonoids formononetin and genistein caused severe reduction in root formation. Also, the relative expression of several transcription factors was analysed in 1-week-old NAA-treated explants (stem cell niche formation stage), in NAA- and BAP-treated explants (no root formation), and in the roots of germinated seeds. The results showed, for the first time in a legume, that the transcription factors homeodomain WOX5 and the AP2-domain containing PLETHORA1 and 2, BABY BOOM1 were strongly induced by auxin addition, while cytokinin addition dramatically reduced their expression, indicating a role for these genes in the formation of root stem cell niches.
Plants infected with biotrophic fungal pathogens exhibit reduced photosynthetic rates, nutrient mobilization towards infection sites and, in interactions where discrete pustules are formed, green islands are induced. The ability of cytokinins to mobilize nutrients towards sites of application and to delay senescence led researchers to speculate that cytokinins might be involved in nutrient mobilization and green island formation in plants infected with biotrophic fungi. There is evidence that the reduction in photosynthesis in infected leaves results from early increases in invertase activity, leading to carbohydrate accumulation and the downregulation of photosynthetic metabolism. In this Opinion article, we propose that these seemingly disparate changes in host physiology in infected plants are the result of cytokinin-induced increases in invertase activity occurring early on in the host-pathogen interaction.