The TCP class of genes is found only in plants and is represented by the first three identified genes: teosinte branched1, cycloidea and pcf. Members belonging to this class are important regulators of plant growth, development and control multiple traits in diverse plant species, including flower and petal asymmetry, plant architecture, leaf morphogenesis and senescence, embryo growth and circadian rhythm. Here we described a member of the TCP-P subfamily called AtTCP23. Using qRT-PCR we present evidence that AtTCP23 is ubiquitously express in all organs examined. To ascertain AtTCP23 localization, we fused GFP at the C-terminal position and analyzed stable expression by confocal microscopy. Transgenic lines harboring the full-length protein (OxTCP23:GFP) seems to accumulate GFP in the nucleus. In order to analyze AtTCP23 function, we obtained a T-DNA insertional line and developed AtTCP23 over-expression (OxTCP23) lines. Phenotypic analysis indicates that tcp23-1 knockout line has an early-flowering phenotype while overexpression lines (OxTCP23 and OxTCP23:eGFP) presents opposite phenotype. Besides that those lines have leaf morphology alteration, pale leaf borders and smaller roots. Thus we propose in this study that AtTCP23 may be involved in flowering time control and plant development.
Metazoans and plants use pattern recognition receptors (PRRs) to sense conserved microbial-associated molecular patterns (MAMPs) in the extracellular environment. In plants, the bacterial MAMPs flagellin and elongation factor Tu (EF-Tu) activate distinct, phylogenetically related cell surface pattern recognition receptors of the leucine-rich repeat receptor kinase (LRR-RK) family called FLS2 and EF-Tu receptor, respectively. BAK1 is an LRR-RK coreceptor for both FLS2 and EF-Tu receptor. BAK1 is also a coreceptor for the plant brassinosteroid (BR) receptor, the LRR-RK BRI1. Binding of BR to BRI1 primarily promotes cell elongation. Here, we tune the BR pathway response to establish how plant cells can generate functionally different cellular outputs in response to MAMPs and pathogens. We demonstrate that BR can act antagonistically or synergistically with responses to MAMPs. We further show that the synergistic activities of BRs on MAMP responses require BAK1. Our results highlight the importance of plant steroid homeostasis as a critical step in the establishment of plant immunity. We propose that tradeoffs associated with plasticity in the face of infection are layered atop plant steroid developmental programs.
Receptor kinases with leucine-rich repeat (LRR) extracellular domains form the largest family of receptors in plants. In the few cases for which there is mechanistic information, ligand binding in the extracellular domain often triggers the recruitment of a LRR-coreceptor kinase. The current model proposes that this recruitment is mediated by their respective kinase domains. Here, we show that the extracellular LRR domain of BRI1-ASSOCIATED KINASE1 (BAK1), a coreceptor involved in the disparate processes of cell surface steroid signaling and immunity in plants, is critical for its association with specific ligand-binding LRR-containing receptors. The LRRs of BAK1 thus serve as a platform for the molecular assembly of signal-competent receptors. We propose that this mechanism represents a paradigm for LRR receptor activation in plants.
The translocator protein 18 kDa (TSPO), previously known as the peripheral-type benzodiazepine receptor (PBR), is important for many cellular functions in mammals and bacteria, such as steroid biosynthesis, cellular respiration, cell proliferation, apoptosis, immunomodulation, transport of porphyrins and anions. Arabidopsis thaliana contains a single TSPO/PBR-related gene with a 40 amino acid N-terminal extension compared to its homologs in bacteria or mammals suggesting it might be chloroplast or mitochondrial localized.
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