Delayed degradation of chlorophylls and photosynthetic proteins in Arabidopsis autophagy mutants during stress-induced leaf yellowing

Under mild abiotic-stress conditions, Arabidopsis atg mutants showed a functional stay-green phenotype which is probably caused by the lack of chloroplastic autophagy and the retrograde regulation of senescence-associated gene expressio

Light-Mediated Regulation of Leaf Senescence

Light is the primary regulator of various biological processes during the plant life cycle. Although plants utilize photosynthetically active radiation to generate chemical energy, they possess several photoreceptors that perceive light of specific wavelengths and then induce wavelength-specific responses. Light is also one of the key determinants of the initiation of leaf senescence, the last stage of leaf development. As the leaf photosynthetic activity decreases during the senescence phase, chloroplasts generate a variety of light-mediated retrograde signals to alter the expression of nuclear genes. On the other hand, phytochrome B (phyB)-mediated red-light signaling inhibits the initiation of leaf senescence by repressing the phytochrome interacting factor (PIF)-mediated transcriptional regulatory network involved in leaf senescence. In recent years, significant progress has been made in the field of leaf senescence to elucidate the role of light in the regulation of nuclear gene expression at the molecular level during the senescence phase. This review presents a summary of the current knowledge of the molecular mechanisms underlying light-mediated regulation of leaf senescence

Functional analysis of N-terminal domains of Arabidopsis chlorophyllide a oxygenase

Higher plants acclimate to various light environments by changing the antenna size of a light harvesting photosystem. The antenna size of a photosystem is partly determined by the amount of chlorophyll b in the light-harvesting complexes. Chlorophyllide a oxygenase (CAO) converts chlorophyll a to chlorophyll b in a two-step oxygenation reaction. In our previous study, we demonstrated that the cellular level of the CAO protein controls accumulation of chlorophyll b. We found that the amino acids sequences of CAO in higher plants consist of three domains (A, B, and C domains). The C domain exhibits a catalytic function, and we demonstrated that the combination of the A and B domains regulates the cellular level of CAO. However, the individual function of each of A and B domain has not been determined yet. Therefore, in the present study we constructed a series of deleted CAO sequences that were fused with green fluorescent protein and overexpressed in a chlorophyll b-less mutant of Arabidopsis thaliana, ch1-1, to further dissect functions of A and B domains. Subsequent comparative analyses of the transgenic plants overexpressing B-domain containing proteins and those lacking the B domain determined that there was no significant difference in CAO protein levels. These results indicate that the B domain is not involved in the regulation of the CAO protein levels. Taken together, we concluded that the A domain alone is involved in the regulatory mechanism of the CAO protein levels

Salt treatments and induction of senescence

High salinity, one of the most severe abiotic stresses encountered by land plants, often results from water deficit and also induces whole-plant senescence. Thus, salt treatment provides a useful technique for stress-mediated induction of senescence in plants. In this chapter, we describe the procedures to induce senescence in Arabidopsis (Arabidopsis thaliana) and rice (Oryza sativa), using NaCl or KCl. Furthermore, we present experimental approaches to measure salt stress-induced leaf senescence.© Springer Science+Business Media, LLC 2008.N

The Divergent Roles of STAYGREEN (SGR) Homologs in Chlorophyll Degradation

This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/.Degradation of chlorophyll (Chl) by Chl catabolic enzymes (CCEs) causes the loss of green color that typically occurs during senescence of leaves. In addition to CCEs, STAYGREEN1 (SGR1) functions as a key regulator of Chl degradation. Although sgr1 mutants in many plant species exhibit a staygreen phenotype, the biochemical function of the SGR1 protein remains elusive. Many recent studies have examined the physiological and molecular roles of SGR1 and its homologs (SGR2 and SGR-LIKE) in Chl metabolism, finding that these proteins have different roles in different species. In this review, we summarize the recent studies on SGR and discuss the most likely functions of SGR homologs.OAIID:oai:osos.snu.ac.kr:snu2015-01/102/0000003606/4ADJUST_YN:YEMP_ID:A002118DEPT_CD:517CITE_RATE:2.09FILENAME:2015-4 sgr minireview (mol cells).pdfDEPT_NM:식물생산과학부SCOPUS_YN:YCONFIRM:

Editorial: Regulatory Mechanisms of Leaf Senescence Under Environmental Stresses

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Roles of rice PHYTOCHROME-INTERACTING FACTOR-LIKE1 (OsPIL1) in leaf senescence

Rice (Oryza sativa) Phytochrome-Interacting Factor-Like1 (OsPIL1), a basic helix-loop-helix transcription factor, plays an important role in the elongation of internode cells. Recently, we found that OsPIL1 participates in chlorophyll biosynthesis by directly upregulating several genes encoding components of the photosystem apparatus. Here, we show that OsPIL1 negatively regulates leaf senescence in rice. During dark-induced senescence (DIS), ospil1 mutants senesced earlier than wild type; this is opposite to mutants of Arabidopsis PIF4 and PIF5, the closest homologs of OsPIL1. Microarray analysis revealed that during DIS, several senescence-associated genes were upregulated and OsGLKs, negative regulators of leaf senescence, were strongly repressed in ospil1 mutants. Transgenic Arabidopsis plants overexpressing OsPIL1 showed an early senescing phenotype during DIS. In addition, OsPIL1 expressed in Arabidopsis upregulates the transcription of ORESARA1, a major senescence-inducing NAC transcription factor and one of the downstream genes of Arabidopsis PIF4, by directly binding the promoter region. These results indicate that OsPIL1 and Arabidopsis PIF4 have similar functions, but their downstream regulatory cascades have opposite effects.OAIID:RECH_ACHV_DSTSH_NO:T201714807RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A002118CITE_RATE:0FILENAME:2017 OsPIL1 leaf senescence-PSB.pdfDEPT_NM:식물생산과학부EMAIL:[email protected]_YN:YFILEURL:https://srnd.snu.ac.kr/eXrepEIR/fws/file/16e01931-13eb-47f8-8934-9cd448144ec1/linkN