TY  - JOUR
A1  - Zhao, Liming
A1  - Xia, Yan
A1  - Wu, Xiao-Yuan
A1  - Schippers, Jos H. M.
A1  - Jing, Hai-Chun
T1  - Phenotypic analysis and molecular markers of leaf senescence
JF  - Plant Senescence: Methods and Protocols
N2  - The process of leaf senescence consists of the final stage of leaf development. It has evolved as a mechanism to degrade macromolecules and micronutrients and remobilize them to other developing parts of the plant; hence it plays a central role for the survival of plants and crop production. During senescence, a range of physiological, morphological, cellular, and molecular events occur, which are generally referred to as the senescence syndrome that includes several hallmarks such as visible yellowing, loss of chlorophyll and water content, increase of ion leakage and cell death, deformation of chloroplast and cell structure, as well as the upregulation of thousands of so-called senescence-associated genes (SAGs) and downregulation of photosynthesis-associated genes (PAGs). This chapter is devoted to methods characterizing the onset and progression of leaf senescence at the morphological, physiological, cellular, and molecular levels. Leaf senescence normally progresses in an age-dependent manner but is also induced prematurely by a variety of environmental stresses in plants. Focused on the hallmarks of the senescence syndrome, a series of protocols is described to asses quantitatively the senescence process caused by developmental cues or environmental perturbations. We first briefly describe the senescence process, the events associated with the senescence syndrome, and the theories and methods to phenotype senescence. Detailed protocols for monitoring senescence in planta and in vitro, using the whole plant and the detached leaf, respectively, are presented. For convenience, most of the protocols use the model plant species Arabidopsis and rice, but they can be easily extended to other plants.
KW  - Leaf senescence
KW  - Visible yellowing
KW  - Chlorophyll
KW  - Ion leakage
KW  - Cell death
KW  - Senescence-associated genes (SAGs)
KW  - Arabidopsis
KW  - Rice
Y1  - 2018
SN  - 978-1-4939-7672-0
SN  - 978-1-4939-7670-6
U6  - https://doi.org/10.1007/978-1-4939-7672-0_3
SN  - 1064-3745
SN  - 1940-6029
VL  - 1744
SP  - 35
EP  - 48
PB  - Humana Press Inc.
CY  - Totowa
ER  - 
TY  - JOUR
A1  - Köslin-Findeklee, Fabian
A1  - Rizi, Vajiheh Safavi
A1  - Becker, Martin A.
A1  - Parra-Londono, Sebastian
A1  - Arif, Muhammad
A1  - Balazadeh, Salma
A1  - Müller-Röber, Bernd
A1  - Kunze, Reinhard
A1  - Horst, Walter J.
T1  - Transcriptomic analysis of nitrogen starvation- and cultivar-specific leaf senescence in winter oilseed rape (Brassica napus L.)
JF  - Plant science : an international journal of experimental plant biology
N2  - High nitrogen (N) efficiency, characterized by high grain yield under N limitation, is an important agricultural trait in Brassica napus L. cultivars related to delayed senescence of older leaves during reproductive growth (a syndrome called stay-green). The aim of this study was thus to identify genes whose expression is specifically altered during N starvation-induced leaf senescence and that can be used as markers to distinguish cultivars at early stages of senescence prior to chlorophyll loss. To this end, the transcriptomes of leaves of two B. napus cultivars differing in stay-green characteristics and N efficiency were analyzed 4 days after the induction of senescence by either N starvation, leaf shading or detaching. In addition to N metabolism genes, N starvation mostly (and specifically) repressed genes related to photosynthesis, photorespiration and cell-wall structure, while genes related to mitochondrial electron transport and flavonoid biosynthesis were predominately up-regulated. A kinetic study over a period of 12 days with four B. napus cultivars differing in their stay-green characteristics confirmed the cultivar-specific regulation of six genes in agreement with their senescence behavior: the senescence regulator ANAC029, the anthocyanin synthesis-related genes ANS and DFR-like1, the ammonium transporter AMT1:4, the ureide transporter UPSS, and SPS1 involved in sucrose biosynthesis. The identified genes represent markers for the detection of cultivar-specific differences in N starvation-induced leaf senescence and can thus be employed as valuable tools in B. napus breeding. (C) 2015 Elsevier Ireland Ltd. All rights reserved.
KW  - Brassica napus
KW  - Genotypic differences
KW  - Leaf senescence
KW  - Molecular marker
KW  - N efficiency
KW  - Stay-green
Y1  - 2015
U6  - https://doi.org/10.1016/j.plantsci.2014.11.018
SN  - 0168-9452
VL  - 233
SP  - 174
EP  - 185
PB  - Elsevier
CY  - Clare
ER  - 
TY  - THES
A1  - Matallana-Ramírez, Lilian Paola
T1  - Unraveling the ORE1 regulon in Arabidopsis thaliana : molecular and functional characterization of up- and down-stream components
T1  - Aufklärung des ORE1-Regulationsnetzwerks in Arabidopsis thaliana : molekulare und funktionelle Charakterisierung von Über- und untergeordneten Komponenten
N2  - Leaf senescence is an active process required for plant survival, and it is flexibly controlled, allowing plant adaptation to environmental conditions. Although senescence is largely an age-dependent process, it can be triggered by environmental signals and stresses. Leaf senescence coordinates the breakdown and turnover of many cellular components, allowing a massive remobilization and recycling of nutrients from senescing tissues to other organs (e.g., young leaves, roots, and seeds), thus enhancing the fitness of the plant. Such metabolic coordination requires a tight regulation of gene expression. One important mechanism for the regulation of gene expression is at the transcriptional level via transcription factors (TFs). The NAC TF family (NAM, ATAF, CUC) includes various members that show elevated expression during senescence, including ORE1 (ANAC092/AtNAC2) among others. ORE1 was first reported in a screen for mutants with delayed senescence (oresara1, 2, 3, and 11). It was named after the Korean word “oresara,” meaning “long-living,” and abbreviated to ORE1, 2, 3, and 11, respectively. Although the pivotal role of ORE1 in controlling leaf senescence has recently been demonstrated, the underlying molecular mechanisms and the pathways it regulates are still poorly understood. To unravel the signaling cascade through which ORE1 exerts its function, we analyzed particular features of regulatory pathways up-stream and down-stream of ORE1. We identified characteristic spatial and temporal expression patterns of ORE1 that are conserved in Arabidopsis thaliana and Nicotiana tabacum and that link ORE1 expression to senescence as well as to salt stress. We proved that ORE1 positively regulates natural and dark-induced senescence. Molecular characterization of the ORE1 promoter in silico and experimentally suggested a role of the 5’UTR in mediating ORE1 expression. ORE1 is a putative substrate of a calcium-dependent protein kinase named CKOR (unpublished data). Promising data revealed a positive regulation of putative ORE1 targets by CKOR, suggesting the phosphorylation of ORE1 as a requirement for its regulation. Additionally, as part of the ORE1 up-stream regulatory pathway, we identified the NAC TF ATAF1 which was able to transactivate the ORE1 promoter in vivo. Expression studies using chemically inducible ORE1 overexpression lines and transactivation assays employing leaf mesophyll cell protoplasts provided information on target genes whose expression was rapidly induced upon ORE1 induction. First, a set of target genes was established and referred to as early responding in the ORE1 regulatory network. The consensus binding site (BS) of ORE1 was characterized. Analysis of some putative targets revealed the presence of ORE1 BSs in their promoters and the in vitro and in vivo binding of ORE1 to their promoters. Among these putative target genes, BIFUNCTIONAL NUCLEASE I (BFN1) and VND-Interacting2 (VNI2) were further characterized. The expression of BFN1 was found to be dependent on the presence of ORE1. Our results provide convincing data which support a role for BFN1 as a direct target of ORE1. Characterization of VNI2 in age-dependent and stress-induced senescence revealed ORE1 as a key up-stream regulator since it can bind and activate VNI2 expression in vivo and in vitro. Furthermore, VNI2 was able to promote or delay senescence depending on the presence of an activation domain located in its C-terminal region. The plasticity of this gene might include alternative splicing (AS) to regulate its function in different organs and at different developmental stages, particularly during senescence. A model is proposed on the molecular mechanism governing the dual role of VNI2 during senescence.
N2  - Der Alterungsprozess lebender Organismen wird seit vielen Jahren wissenschaftlich untersucht. In Pflanzen wird der Alterungsprozess Seneszenz genannt. Er ist für das Überleben der Pflanze von großer Bedeutung. Dennoch ist unser Wissen über die molekularen Mechanismen der Blattseneszenz, dessen komplexe Steuerung und die Wechselwirkungen mit Umweltsignale noch sehr limitiert. Ein wichtiges Steuerungselement besteht in der Aktivierung bestimmter Transkriptionsfaktoren (TFs) die während der Seneszenz unterschiedlich exprimiert werden. Aus der Literatur ist bekannt, dass Mitglieder der NAC TF Familie (NAM/ATAF/CUC) an der Regulation der Seneszenz bei Pflanzen beteiligt sind. ORE1 (ANAC092/AtNAC2), ein NAC TF mit erhöhter Genexpression während der Seneszenz, wurde erstmals in Mutanten mit verzögerte Seneszenz beschrieben, die molekularen Mechanismen, wie ORE1 die Seneszenz kontrolliert und die Stoffwechselwege reguliert, sind aber noch weitgehend unbekannt. Die Arbeiten im Rahmen dieser Dissertation wurden durchgeführt, um einen tieferen Einblick in die Regulationsmechanismen von ORE1 auf natürliche, dunkel induzierte sowie Salzstress-induzierte Seneszenz zu erhalten. Ergebnisse von Untersuchungen an zwei unterschiedlichen Pflanzenspezies (Arabidopsis thalinana und Nicotiana tabacum) deuten auf ein ähnliches Expressionsmuster von ORE1 während der natürlichen als auch der Salz-induzierten Seneszenz hin. In der Promotorregion von ORE1 wurde ein für natürliche Seneszenz charakteristisches Muster identifiziert. In vivo Analysen ergaben darüber hinaus. Hinweise auf zwei weitere ORE1 Regulatoren. Debei handelt es sich umeinen weiteren NAC TF (ATAF1) und (ii) CKOR, einer Calcium-abhängige Protein-Kinase (CDPK).In weiteren Studien wurden sechs Gene identifiziert, die durch ORE1 reguliert werden. In den Promotoren dieser Gene wurden entsprechende Bindestellen für ORE1 lokalisiert. Die ORE1-Bindung an die Promotoren wurde daraufhin sowohl in vitro als auch in vivo verifiziert. Zwei dieser Gene, die BIFUNCTIONAL Nuclease I (BFNI) und VND-Interacting2 (VNI2), wurden zudem auf molekularer und physiologischer Ebene untersucht.
KW  - Blattalterung
KW  - Transkriptionsfaktor
KW  - Regulationsweg
KW  - Leaf senescence
KW  - transcription factor
KW  - regulatory pathway
Y1  - 2012
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-62646
ER  -