Project description:A cascade of basic helix-loop-helix transcription factors guide tapetal cell development in maize anthers, using proteins conserved in Arabidopsis and rice but deployed with a distinctive timing. Anthers were dissected and staged to be 1500 μm in length (+/- 100 μm) and samples were compared between mutants and fertile siblings on an Agilent 4x44 custom microarray. Analysis included MS32 which is another basic helix-loop-helix factor that acts later during tapetal differentiation.
Project description:Stomata open in response to light and close following exposure to abscisic acid (ABA). They regulate gas exchange between plants and atmosphere, allowing plants to adapt to changing environmental conditions. ABA binding to receptors initiates a signaling cascade that involves protein phosphorylation. Here we show that ABA induced phosphorylation of three basic helix-loop-helix (bHLH) transcription factors, called AKSs (ABA-RESPONSIVE KINASE SUBSTRATES; AKS1, AKS2, AKS3), in Arabidopsis guard cells, and that they facilitated stomatal opening through the transcription of genes encoding inwardly-rectifying K+ channels. aks1aks2-1 double mutant plants showed decreases in light-induced stomatal opening, K+ accumulation in response to light, activity of inwardly-rectifying K+ channels, and transcription of genes encoding major inwardly-rectifying K+ channels. Overexpression of POTASSIUM CHANNEL IN ARABIDOPSIS THALIANA 1 (KAT1), which encodes a major inwardly-rectifying K+ channel in guard cells, rescued the phenotype of aks1aks2-1 plants. AKS1 bound directly to the promoter of KAT1, an interaction that was attenuated after ABA-induced phosphorylation. The ABA agonist pyrabactin induced phosphorylation of AKSs. Our results demonstrate that the AKS family of bHLH transcription factors facilitates stomatal opening through transcription of genes encoding inwardly-rectifying K+ channels, and that ABA suppresses the activity of inwardly-rectifying K+ channel activity by triggering the phosphorylation of these transcription factors. To find the affect of AKS1 and AKS2 transcription factors on gene expression, Arabidopsis guard cell protoplasts from wild type and aks1aks2-1 mutant were compared. Three independent experiments were performed.
Project description:Stomata are highly specialized organs which consist of pairs of guard cells and regulate gas and water vapor exchange in plants. While early stages of guard cell differentiation have been described and were interpreted in analogy to processes of cell type differentiation in animals, the downstream development of functional stomatal guard cells remains poorly understood. We have isolated an Arabidopsis mutant, scap1 (stomatal carpenter 1), that develops irregularly shaped guard cells and lacks the ability to control stomatal aperture, including CO2-induced stomatal closing and light-induced stomatal opening. SCAP1 was identified as a plant-specific Dof-type transcription factor expressed in maturing guard cells but not in guard mother cells. SCAP1 regulates the expression of genes encoding key elements of stomatal functioning and morphogenesis, such as a K+ channel protein, MYB60 transcription factor, and pectin methyl esterase. Consequently, ion homeostasis was disturbed in scap1 guard cells, and esterification of extracellular pectins was impaired so that the cell walls lining the pores did not mature normally. We conclude that SCAP1 regulates essential processes of stomatal guard cell maturation and functions as a key transcription factor regulating the final stages of guard cell differentiation.
Project description:Stomata are highly specialized organs which consist of pairs of guard cells and regulate gas and water vapor exchange in plants. While early stages of guard cell differentiation have been described and were interpreted in analogy to processes of cell type differentiation in animals, the downstream development of functional stomatal guard cells remains poorly understood. We have isolated an Arabidopsis mutant, scap1 (stomatal carpenter 1), that develops irregularly shaped guard cells and lacks the ability to control stomatal aperture, including CO2-induced stomatal closing and light-induced stomatal opening. SCAP1 was identified as a plant-specific Dof-type transcription factor expressed in maturing guard cells but not in guard mother cells. SCAP1 regulates the expression of genes encoding key elements of stomatal functioning and morphogenesis, such as a K+ channel protein, MYB60 transcription factor, and pectin methyl esterase. Consequently, ion homeostasis was disturbed in scap1 guard cells, and esterification of extracellular pectins was impaired so that the cell walls lining the pores did not mature normally. We conclude that SCAP1 regulates essential processes of stomatal guard cell maturation and functions as a key transcription factor regulating the final stages of guard cell differentiation. We isolated guard cell protoplasts from 4-week-old WT(Col-0) and scap1 mutant plants and extracted RNA independently. Four biological replicates were performed for each experiment.