Project description:Chloroplast-nuclear retrograde signaling is viewed as a mechanism for inter-organelle communication. Here we show the SAL1-PAP (3′-phosphoadenosine 5′- phosphate) retrograde pathway functions more broadly in guard cells, interacting with abscisic acid (ABA) signaling at least in part via exoribonucleases. Unexpectedly, PAP bypasses the canonical signaling components ABA Insensitive 1 (ABI1) and Open Stomata 1 (OST1) by priming an alternative pathway that restores ABA-responsive gene expression, ROS bursts, ion channel function and stomatal closure in ost1-2. This alternative pathway up-regulates lowly expressed Calcium Dependent Protein Kinases (CDPKs) which have the capacity to activate the key slow anion channel SLAC1 in response to ABA-mediated and ost1-2 independent calcium release. The role of PAP in priming an alternative pathway to bypass components previously considered essential for stomatal closure demonstrates how a chloroplast signal can have broader roles as a secondary messenger to directly intersect with and tune hormone signaling.
Project description:Transcriptome profiling of WT, mbd1, pyl5 and mbd1 pyl5 knock-out mutants in response to Abscisic acid (ABA) was done using Affymetrix GenechipTM Arabidopsis ATH1 Genome Array.
Project description:Stresses that target mitochondrial function lead to altered transcriptional responses for 100-1000s of genes genome wide, and are signalled via retrograde signalling pathways within the cell. rao1 mutants contain a mutation in a gene encoding a Cyclin-Dependant Kinase E;1 and cannot induce stress responsive genes (such as the mitochondrial alternative oxidase 1a) in response to mitochondrial dysfunction. We sought to define the global gene network regulated through RAO1 function in response to mitochondrial stress (mimicked through treatment of plants with antimycin A - a specific inhibitor of complex III in the mitochondrial electron transfer chain). We have defined global stress responses that are positively and negatively mediated by RAO1 function, as well as global stress responses to antimycin A treatment that are regulated independently of RAO1. We used Affymetrix microarray to characterise global gene expression profiles for mutant plants with compromised mitochondrial retrograde signalling under stress (rao1 mutants), to define the genome wide transcriptional network regulated through RAO1 function. rao1 and wild type 14-day-old seedlings (the optimal stage as defined by forward genetic screens that identifed rao1 mutants) grown on GamborgB5 plates were treated by spraying plants with 50 µM antimycin A (an elicitor of mitochondrial retrograde signalling) while mock control samples were sprayed with deionised water. Samples were collected after 3hr of treatment for global expression profiling.
Project description:To identify genes of the guard cell transkriptome of Arabidopsis thaliana enriched guard cell samples were compared with total leaf tissue. Genes of the abscisic acid and humidity response of Arabidopsis thaliana guard cells were identified by treatment with ABA-Spray and low humidity. Ost1-2 and slac1-3 mutants were compared to their wildtype.
