Project description:gene expression profiling in different zones along the gradient of the growing maize leaf balde aover a time course of dirunal cycle and carbon starvation by extension of the night Plants assimilate carbon in their photosynthetic tissues in the light. However, carbon is required during the night, and in non-photosynthetic organs. It is therefore essential that plants manage their carbon resources spatially and temporally and coordinate growth with carbon availability. In growing maize (Zea mays) leaf blades a defined developmental gradient facilitates analyses in the cell division, elongation and mature zones. We investigated the responses of the metabolome and transcriptome and polysome loading, as a qualitative proxy for protein synthesis, at dusk, dawn and 6, 14 and 24 hours into an extended night, and tracked whole leaf elongation over this time course. Starch and sugars are depleted by dawn in the mature zone, but only after an extension of the night in the elongation and division zones. Sucrose recovers partially between 14 and 24 h into the extended night in the growth zones but not the mature zone. The global metabolome and transcriptome track these zone-specific changes in sucrose. Leaf elongation and polysome loading in the growth zones also remain high at dawn, decrease between 6 and 14 h into the extended night and then partially recover indicating that growth processes are determined by local carbon status. The level of sucrose-signaling metabolite trehalose-6-phosphate, and the trehalose-6-phosphate:sucrose ratio are much higher in growth than mature zones at dusk and dawn but fall in the extended night. Candidate genes were identified by searching for transcripts that show characteristic temporal response patterns or contrasting responses to carbon starvation in growth and mature zones.
Project description:gene expression profiling in different zones along the gradient of the growing maize leaf balde aover a time course of dirunal cycle and carbon starvation by extension of the night Plants assimilate carbon in their photosynthetic tissues in the light. However, carbon is required during the night, and in non-photosynthetic organs. It is therefore essential that plants manage their carbon resources spatially and temporally and coordinate growth with carbon availability. In growing maize (Zea mays) leaf blades a defined developmental gradient facilitates analyses in the cell division, elongation and mature zones. We investigated the responses of the metabolome and transcriptome and polysome loading, as a qualitative proxy for protein synthesis, at dusk, dawn and 6, 14 and 24 hours into an extended night, and tracked whole leaf elongation over this time course. Starch and sugars are depleted by dawn in the mature zone, but only after an extension of the night in the elongation and division zones. Sucrose recovers partially between 14 and 24 h into the extended night in the growth zones but not the mature zone. The global metabolome and transcriptome track these zone-specific changes in sucrose. Leaf elongation and polysome loading in the growth zones also remain high at dawn, decrease between 6 and 14 h into the extended night and then partially recover indicating that growth processes are determined by local carbon status. The level of sucrose-signaling metabolite trehalose-6-phosphate, and the trehalose-6-phosphate:sucrose ratio are much higher in growth than mature zones at dusk and dawn but fall in the extended night. Candidate genes were identified by searching for transcripts that show characteristic temporal response patterns or contrasting responses to carbon starvation in growth and mature zones. 3 repliucates per time point and leaf region, each pooled form 5 indiviual plants
Project description:Transcriptome of three zones (from the base to 3.5 cm, from 3.5 to 7.0 cm and from 7.0 to 10.5 cm) of the developing fourth leaf of maize B104 plants was profiled at two days after leaf appearance (DALA). Only leaf samples were taken for well-watered plants.
Project description:To investigate the developmental gradient of the third maize leaf, the light exposed area of the leaf (corresponding to 18cm of leaf) and 2cm shaded by the sheath were sampled in ten slices. Four replicates were collected, immediately shock frozen in liquid nitrogen and subsequently cut into 2cm slices. At least 10 plants were pooled for each biological replicate. We have systematically analyzed a developmental gradient of the third maize leaf from the point of emergence into the light to the tip in ten continuous leaf slices to study organ development and physiological and biochemical functions. Transcriptome analysis, oxygen sensitivity of photosynthesis, delta-13C values, and photosynthetic rate measurements showed that the maize leaf undergoes a sink to source transition without an intermediate phase of C3 photosynthesis or operation of a photorespiratory carbon pump. Metabolome and transcriptome analysis, chlorophyll and protein measurements, as well as dry weight determination showed continuous gradients for all analyzed items. The absence of binary on-off switches and regulons pointed to a morphogradient along the leaf as the determining factor of developmental stage. Analysis of transcription factors for differential expression along the leaf gradient defined a list of putative regulators orchestrating the sink-to-source transition and establishment of C4 photosynthesis. Finally, transcriptome and metabolome analysis, as well as enzyme activity measurements, and absolute quantification of selected metabolites revised the current model of maize C4 photosynthesis. All datasets are included within the publication to serve as a resource for maize leaf systems biology. For the transcriptional analysis, the goal of the study was to (i) identify whether the leaf contains binary switches for genes involved in photosynthesis, (ii)characterize the patterns of gene expression in the leaf, (iii) provide independent validation of maize leaf expression experiments published in Li et al. (2011) and (iv) determine transcripts co-expressed with key transcripts of C4 photosynthesis. To this end, changed transcripts were determined by ANOVA and characterized by K-means and hierachical clustering.
Project description:To investigate the developmental gradient of the third maize leaf, the light exposed area of the leaf (corresponding to 18cm of leaf) and 2cm shaded by the sheath were sampled in ten slices. Four replicates were collected, immediately shock frozen in liquid nitrogen and subsequently cut into 2cm slices. At least 10 plants were pooled for each biological replicate. We have systematically analyzed a developmental gradient of the third maize leaf from the point of emergence into the light to the tip in ten continuous leaf slices to study organ development and physiological and biochemical functions. Transcriptome analysis, oxygen sensitivity of photosynthesis, delta-13C values, and photosynthetic rate measurements showed that the maize leaf undergoes a sink to source transition without an intermediate phase of C3 photosynthesis or operation of a photorespiratory carbon pump. Metabolome and transcriptome analysis, chlorophyll and protein measurements, as well as dry weight determination showed continuous gradients for all analyzed items. The absence of binary on-off switches and regulons pointed to a morphogradient along the leaf as the determining factor of developmental stage. Analysis of transcription factors for differential expression along the leaf gradient defined a list of putative regulators orchestrating the sink-to-source transition and establishment of C4 photosynthesis. Finally, transcriptome and metabolome analysis, as well as enzyme activity measurements, and absolute quantification of selected metabolites revised the current model of maize C4 photosynthesis. All datasets are included within the publication to serve as a resource for maize leaf systems biology. For the transcriptional analysis, the goal of the study was to (i) identify whether the leaf contains binary switches for genes involved in photosynthesis, (ii)characterize the patterns of gene expression in the leaf, (iii) provide independent validation of maize leaf expression experiments published in Li et al. (2011) and (iv) determine transcripts co-expressed with key transcripts of C4 photosynthesis. To this end, changed transcripts were determined by ANOVA and characterized by K-means and hierachical clustering. Four replicates were collected for each of the ten consecutive leaf slices resulting in 40 one color arrays. Slice 1 represents the tip of the leaf, slice 10 the lowermost slice which is shaded by the sheath with all slices in between consecutively numbered.
Project description:C4 grasses, such as maize (Zea mays), have high photosynthetic efficiency through combined biochemical and structural adaptations.C4 photosynthesis is established along the developmental axis of the leafblade, leading from an undifferentiated leaf base just above the ligule into highly specialized mesophyll cells (MCs) and bundle sheath cells (BSCs) at the tip. To resolve the kinetics of maize leaf development and C4 differentiation and to obtain a systems-level understanding of maize leaf formation, the accumulation profiles of proteomes of the leaf and the isolated BSCs with their vascular bundle along the developmental gradient were determined using large-scale mass spectrometry. This was complemented by extensive qualitative and quantitative microscopy analysis of structural features (e.g., Kranz anatomy, plasmodesmata, cell wall, and organelles). More than 4300 proteins were identified and functionally annotated. Developmental protein accumulation profiles and hierarchical cluster analysis then determined the kinetics of organelle biogenesis, formation of cellular structures, metabolism, and coexpression patterns. Two main expression clusters were observed, each divided in subclusters, suggesting that a limited number of developmental regulatory networks organize concerted protein accumulation along the leaf gradient. The coexpression with BSC and MC markers provided strong candidates for further analysis of C4 specialization, in particular transporters and biogenesis factors. Based on the integrated information, we describe five developmental transitions that provide a conceptual and practical template for further analysis. An online protein expression viewer is provided through the PlantProteomeDatabase.
Project description:Maize and rice are the two most economically important grass crops and utilize distinct forms of photosynthesis to fix carbon: C4 and C3 respectively. Relative to C3 photosynthesis, C4 photosynthesis reduces photorespiration and affords higher water and nitrogen use efficiencies under hot arid conditions. To define key innovations in C4 photosynthesis, we profiled metabolites and gene expression along a developing leaf gradient. A novel statistical method was implemented to compare transcriptomes from these two species along a unified leaf developmental gradient and define candidate cis-regulatory elements and transcription factors driving photosynthetic gene expression. We also present comparative primary and secondary metabolic profiles along the gradients that provide new insight into nitrogen and carbon metabolism in C3 and C4 grasses. These resources, including community viewers to access and mine these datasets, will enable the elucidation and engineering of C4 photosynthetic networks to improve the photosynthetic capacity of C3 and C4 grasses.
Project description:Maize and rice are the two most economically important grass crops and utilize distinct forms of photosynthesis to fix carbon: C4 and C3 respectively. Relative to C3 photosynthesis, C4 photosynthesis reduces photorespiration and affords higher water and nitrogen use efficiencies under hot arid conditions. To define key innovations in C4 photosynthesis, we profiled metabolites and gene expression along a developing leaf gradient. A novel statistical method was implemented to compare transcriptomes from these two species along a unified leaf developmental gradient and define candidate cis-regulatory elements and transcription factors driving photosynthetic gene expression. We also present comparative primary and secondary metabolic profiles along the gradients that provide new insight into nitrogen and carbon metabolism in C3 and C4 grasses. These resources, including community viewers to access and mine these datasets, will enable the elucidation and engineering of C4 photosynthetic networks to improve the photosynthetic capacity of C3 and C4 grasses. [Maize] Nine day old third leaves of maize were cut into fifteen 1 cm segments; samples were pooled from an average of seven plants per biological replicate and six biological replicates in total were collected on different dates. [Rice] 14 day old third leaves of rice were cut into eleven 2 cm segments, samples were pooled from an average of 15 plants per biological replicate and four replicates in total were collected.