Developmental and Age-Related Processes That Influence the Longevity and Senescence of Photosynthetic Tissues in Arabidopsis

Hensel, Linda L.; Grbić, Vojislava; Baumgarten, David A.; Bleecker, Anthony B.

doi:10.2307/3869710

Cited by 68 publications

(83 citation statements)

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“…While regulation of transcription has been implicated in some of these processes, post-transcriptional control is often a primary regulatory determinant (21,23,26,29,31,32). This current study indicates that post-transcriptional control was utilized as a primary mechanism when RbcS gene expression was adapted for the specialized cell-type specific expression that provides the foundation for the C 4 pathway in F. bidentis leaves.…”

Section: Discussionmentioning

confidence: 71%

“…Rubisco genes are known to be highly regulated; in many plants their expression is modulated by light (18,23,24), development (20,25,26), cell type (6, 9, 16), photosynthetic metabolism (17,19,(27)(28)(29), and even pathogen infection (30). While regulation of transcription has been implicated in some of these processes, post-transcriptional control is often a primary regulatory determinant (21,23,26,29,31,32).…”

Section: Discussionmentioning

confidence: 99%

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Untranslated Regions of FbRbcS1 mRNA Mediate Bundle Sheath Cell-specific Gene Expression in Leaves of a C4 Plant

Patel¹,

Siegel

Berry

2006

Journal of Biological Chemistry

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C 4 photosynthesis typically requires two specialized leaf cell types, bundle sheath (bs) and mesophyll (mp), which provide the foundation for this highly efficient carbon assimilation pathway. In leaves of Flaveria bidentis, a dicotyledonous C 4 plant, ribulose 1,5-bisphosphate carboxylase (rubisco) accumulates only in bs cells surrounding the vascular centers and not in mp cells. This is in contrast to the more common C 3 plants, which accumulate rubisco in all photosynthetic cells. Many previous studies have focused on transcriptional control of C 4 cell type-specificity; however, post-transcriptional regulation has also been implicated in the bs-specific expression of genes encoding the rubisco subunits. In this current study, a biolistic leaf transformation assay has provided direct evidence that the 5-and 3-untranslated regions (UTRs) of F. bidentis FbRbcS1 mRNA (from a nuclear gene encoding the rubisco small subunit), in themselves, confer strong bs cell-specific expression to gfpA reporter gene transcripts when transcribed from a constitutive CaMV promoter. In transformed leaf regions, strong bs cell-specific GFP expression was accompanied by corresponding bs cellspecific accumulation of the constitutively transcribed FbRbcS1 5-UTR-gfpA-3-UTR mRNAs. Control constructs lacking any RbcS mRNA sequences were expressed in all leaf cell types. These findings demonstrate that characteristic cell type-specific FbRbcS1 expression patterns in C 4 leaves can be established entirely by sequences contained within the transcribed UTRs of FbRbcS1 mRNAs. We conclude that selective transcript stabilization (in bs cells) or degradation (in mp cells) plays a key role in determining bs cell-specific localization of the rubisco enzyme.Plants that utilize the highly efficient C 4 pathway of carbon fixation typically possess a Kranz-type leaf anatomy that consists of two distinct photosynthetic cell types (1-4). Bundle sheath (bs) 3 cells occur as a layer around each leaf vein, while mesophyll (mp) cells occur in one or more layers surrounding the vascular associated rings of bs cells. This specialized leaf anatomy compartmentalizes two sets of photosynthetic reactions that make up the C 4 pathway. In the C 4 dicot Flaveria bidentis, atmospheric CO 2 entering via the leaf stomata is initially incorporated into four carbon acids by phosphoenolpyruvate carboxylase, an enzyme found only in the leaf mp cells. The C 4 acids diffuse from mp cells to bs cells, where they are decarboxylated by a photosynthetic malic enzyme. Within bs chloroplasts, the released CO 2 is incorporated into the Calvin cycle by ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco), the primary enzyme of photosynthetic carbon fixation. The specialized anatomical framework and compartmentalized reactions of the C 4 pathway function as a "CO 2 pump" that concentrates CO 2 in bs cells, where rubisco is specifically localized (1, 2, 5, 6). As a result, the carboxylase activity of this enzyme is increased, while its oxygenase activity, which can decrease phot...

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Section: Discussionmentioning

confidence: 71%

Section: Discussionmentioning

confidence: 99%

Untranslated Regions of FbRbcS1 mRNA Mediate Bundle Sheath Cell-specific Gene Expression in Leaves of a C4 Plant

Patel¹,

Siegel

Berry

2006

Journal of Biological Chemistry

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“…In Arabidopsis, the expression of several senescence-associated genes has been suggested to be directly coupled to the decline of photosynthetic activity, which reduces the cellular sugar levels in leaves (57). Since the transcripts from the E1␤ and E2 subunits accumulated in the senescing leaves, BCKDH may be involved in the utilization of the carbon skeletons of branchedchain amino acids as an energy source during leaf senescence as well as sugar starvation.…”

Section: Discussionmentioning

confidence: 99%

Isolation and Characterization of cDNA Clones for the E1β and E2 Subunits of the Branched-chain α-Ketoacid Dehydrogenase Complex in Arabidopsis

Fujiki

Sato

Ito

et al. 2000

Journal of Biological Chemistry

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Branched-chain ␣-ketoacid dehydrogenase (BCKDH) has been known in mammals to be a key enzyme of the catabolic pathway of branched-chain amino acids. We have isolated two cDNA clones encoding the E1␤ and E2 subunits of BCKDH, respectively, from Arabidopsis thaliana. Proteins encoded in these cDNA sequences had putative mitochondrial targeting sequences and conserved domains reported for their mammalian counterparts. Northern blot and immunoblot analyses showed that transcripts from the respective genes and E2 protein markedly accumulated in leaves kept in the dark. We found that the activity of BCKDH in the leaf extracts also increased when plants were placed in the dark. Addition of sucrose to detached leaves inhibited the accumulation of transcripts, whereas application of a photosynthesis inhibitor strongly induced the expression of these genes even under light illumination. These observations indicate that the cellular sugar level is likely responsible for the dark-induced expression of these genes. The transcript levels of these genes were also high in senescing leaves, in which photosynthetic activity is low and free amino acids from degraded protein are likely to serve as an alternative energy source.The mammalian branched-chain ␣-ketoacid dehydrogenase (BCKDH) 1 is a mitochondrial multienzyme complex that is composed of three subunits carrying different enzymatic activities: branched-chain ␣-ketoacid decarboxylase (E1; EC 1.2.4.4), dihydrolipoyl transacylase (E2; no EC number), and dihydrolipoamide dehydrogenase (E3; EC 1.8.1.4). The E1 subunit is further composed of two E1␣ and two E1␤ subunits. This enzyme complex also contains two specific regulatory enzymes, a kinase and a phosphatase (1). E1 catalyzes the oxidative decarboxylation of branched-chain ␣-keto acids, which are derived from branched-chain amino acids by transamination. E2 catalyzes the transfer of the acyl group from the lipoyl moiety to coenzyme A. E3 is a flavoprotein and reoxidizes the reduced lipoyl sulfur residues of the E2 subunit (2).BCKDH in mammals is thought to be a key enzyme in the catabolism of the branched-chain amino acids, i.e. valine, leucine, and isoleucine. As end products, leucine is converted to acetyl-CoA and acetoacetate, valine to succinyl-CoA, and isoleucine to succinyl-CoA and acetyl-CoA (3). Through this pathway, these amino acids serve as substrates for energy production via acetoacetate and succinyl-CoA. It has been firmly established that nutritional conditions play an important role in modulating the activity of BCKDH through a phosphorylation-dephosphorylation mechanism (4). From this point of view, BCKDH is critically important in the pathway for energy utilization, rather than being merely a system for the catabolism of a small group of amino acids.BCKDH has been extensively studied in mammals because defects in the genes for this enzyme cause maple syrup urine disease, an inborn disorder of metabolism in humans (3). In the plant kingdom, however, we have come across only one case reporting the detection...

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“…Since the elucidation of the genetic control of senescence in leaves has proved difficult (R. Amasino, personal communication), several groups have resorted to molecular approaches to identifying genes likely to be involved in senescence control. Several genes (termed SAG for senescence-associated genes) which show sequence similarity to cysteine proteases are induced early during senescence (32,33). Because (43) showed that enhancing H202 production during the HR led to dramatic increases in the amount of cell death observed in a soybean cell culture system.…”

Section: Senescencementioning

confidence: 99%

Programmed cell death: a way of life for plants.

Greenberg

1996

Proc. Natl. Acad. Sci. U.S.A.

528

322

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Cell death in higher plants has been widely observed in predictable patterns throughout development and in response to pathogenic infection. Genetic, biochemical, and morphological evidence suggests that these cell deaths occur as active processes and can be defined formally as examples of programmed cell death (PCD). Intriguingly, plants have at least two types of PCD, an observation that is also true of PCD in

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Developmental and Age-Related Processes That Influence the Longevity and Senescence of Photosynthetic Tissues in Arabidopsis

Cited by 68 publications

References 0 publications

Untranslated Regions of FbRbcS1 mRNA Mediate Bundle Sheath Cell-specific Gene Expression in Leaves of a C4 Plant

Untranslated Regions of FbRbcS1 mRNA Mediate Bundle Sheath Cell-specific Gene Expression in Leaves of a C4 Plant

Isolation and Characterization of cDNA Clones for the E1β and E2 Subunits of the Branched-chain α-Ketoacid Dehydrogenase Complex in Arabidopsis

Programmed cell death: a way of life for plants.

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