Transcriptome profiling of Arabidopsis mutants of the chlorophyll degradation PAO/Phyllobilin pathway
Ontology highlight
ABSTRACT: Detoxification of chlorophyll during leaf senescence in higher plants is a complex and tightly regulated process. It aims at opening the chlorophyll porphyrin ring to produce non-photoreactive degradation products, termed phyllobilins, which are stored in the vacuole. Here we are describing the influence on the transcriptome of dark-induced senescing leaf of the removal of three key enzymes of the PAO/phyllobilin pathway (namely: PAO, PPH and NYE/SGR).
Project description:Chlorophyll (Chl) degradation is an important process during leaf senescence, bud breaking and fruit ripening. Chlorophyll catabolic pathway has been intensively studied and nearly all the enzymes involved in the pathway are characterized. However, regulatory mechanism of the pathway is largely unknown at the molecular level. In this study, we performed a yeast one-hybrid screening using a library composed only of transcription factor cDNAs to search for factors controlling expression of the chlorophyll catabolic genes. We identified a common regulator, ANAC046, that directly binds to the promoter regions of NON-YELLOW COLORING 1, STAY-GREEN 1 (SGR1), SGR2, and pheophorbide a oxygenase. Transgenic plants overexpressing ANAC046 exhibited an early senescence phenotype with lower chlorophyll content as compared with the wild-type plants, while loss-of-function mutants exhibited a delayed senescence phenotype with higher chlorophyll content. Microarray analysis of ANAC046 showed that not only chlorophyll catabolic genes but also senescence-associated genes were positively regulated by ANAC046. Here, we demonstrate that ANAC046 is a novel positive regulator of Arabidopsis leaf senescence and exerts its effect through controlling the expressions of Chl catabolic genes and senescence-associated genes. Transcriptomes of leaf of ANAC046-overexpression plant (50 days after seed sawing), seedling of ANAC046-SRDX-overexpression plant (5 days after dark treatment), and seedling of ANAC046-knockout plant (5 days after dark treatment) were measured together with their respective wild-type controls.
Project description:Transgenic Arabidopsis thaliana bearing a synthetic degreening circuit were induced to degrade their chlorophyll, and the transcriptomes were profiled at 0, 24, and 48h after degreening induction, as well as in 48h plants that were subsequently allowed to "regreen". Induction of transgene expression resulted in overexpression of the chlorophyll degrading enzymes chorophyllase and PAO (pheide a oxygenase), as well as expression of a diRNA construct to the chlorophyll biosynthetic POR enzymes (NADPH:protochlorophyllide oxidoreductase).
Project description:Monitor changes in the proteome of senescing leaves, using protein MS data obtained from the same leaf groups used for imaging. Arabidopsis thaliana mature leaves were grouped according to their chlorophyll content: Dark Green (DG), Green (G), Light Green (LG) and Yellow (Y), containing 100, 45, 25 and 6.5% chlorophyll relative to DG, respectivelyArabidopsis thaliana mature leaves were grouped according to their chlorophyll content: Dark Green (DG), Green (G), Light Green (LG) and Yellow (Y), containing 100, 45, 25 and 6.5% chlorophyll relative to DG, respectively
Project description:Chlorophyll (Chl) degradation is an important process during leaf senescence, bud breaking and fruit ripening. Chlorophyll catabolic pathway has been intensively studied and nearly all the enzymes involved in the pathway are characterized. However, regulatory mechanism of the pathway is largely unknown at the molecular level. In this study, we performed a yeast one-hybrid screening using a library composed only of transcription factor cDNAs to search for factors controlling expression of the chlorophyll catabolic genes. We identified a common regulator, ANAC046, that directly binds to the promoter regions of NON-YELLOW COLORING 1, STAY-GREEN 1 (SGR1), SGR2, and pheophorbide a oxygenase. Transgenic plants overexpressing ANAC046 exhibited an early senescence phenotype with lower chlorophyll content as compared with the wild-type plants, while loss-of-function mutants exhibited a delayed senescence phenotype with higher chlorophyll content. Microarray analysis of ANAC046 showed that not only chlorophyll catabolic genes but also senescence-associated genes were positively regulated by ANAC046. Here, we demonstrate that ANAC046 is a novel positive regulator of Arabidopsis leaf senescence and exerts its effect through controlling the expressions of Chl catabolic genes and senescence-associated genes.
Project description:Decreasing antenna size is regarded as a potential strategy to improve photosynthesis for higher yield potential. Reducing chlorophyll content has been used as a strategy to decrease antenna size. One of the commonly cited benefits of this strategy has been its ability to improve crop nitrogen use efficiency; however, field evidence for this so far is limited. Here we used a mutant, p35s-Ami-YGL1, which has a lower chlorophyll content and also lower antenna size, to study the impacts of modifying leaf chlorophyll content on tissue nitrogen content and nitrogen use efficiency of plants. We show that the nitrogen contents for different tissues, including the seed tissue, on a weight basis were increased in p35s-Ami-YGL1, together with a decrease in C: N. Concurrently, we found that tissue carbon content decreased, while the content of chlorophyll precursors increased. These results suggest that the observed increase in tissue nitrogen content in Ami-YGL1 does not reflect an increase in plant nitrogen absorption or use efficiency, rather it is a result of stunted carbon fixation capacity of plants. The observed increase in seed nitrogen content in Ami-YGL1 suggests a potential strategy to increase seed nitrogen content in crops.
Project description:The maize inbred line A661 shows a characteristic phenotype when grown at suboptimal temperatures for three weeks and then is exposed to optimal temperatures for one extra week. After this period the third leaf showed two well defined sections: distal (chlorophyll-less; CL) and proximal (chlorophyll-containing; CC) sections. To further investigate the performance of the inbred line A661 under cold conditions a gene expression profiling analysis was conducted using large scale maize microarrays. A total of 1002 transcripts change their expression between both leaf sections and the majority of these codify for proteins located to the chloroplast. Three biological replicates of each leaf sections were analysed. The CC section was used as control.
Project description:To identify the regulatory steps that control chlorophyll accumulation, we compared gene expression in petals and leaves of chrysanthemum cultivars with different chlorophyll levels. Microarray analyses showed that the expression levels of chlorophyll biosynthesis genes encoding glutamyl-tRNA reductase, Mg-protoporphyrin IX chelatase, Mg-protoporphyrin IX monomethylester cyclase, and protochlorophyllorophyllide oxidoreductase were well associated with chlorophyll content: their expression levels were lower in white petals than in green petals, and were highest in leaves. Among chlorophyll catabolic genes, expression of STAY-GREEN, encoding Mg-dechelatase, which is a key enzyme controlling chlorophyll degradation, was considerably higher in white and green petals than in leaves. We searched for transcription factor genes whose expression was well related to chlorophyll level in petals and leaves and found several such genes.
Project description:Detached leaf of mutants from Arabidopsis thaliana mutants from WTcol, TIC55, CYP89a9, MES16 and triple mutant CYP89a9 TIC55 and MES16 incubated in the dark for 3 days.