The timing of maize leaf senescence and characterisation of senescence‐related cDNAs

Smart, Catherine M.; Hosken, Sally E.; Thomas, Howard; Greaves, John; Blair, Bruce G.; Schuch, Wolfgang

doi:10.1111/j.1399-3054.1995.tb05116.x

Cited by 123 publications

(33 citation statements)

References 35 publications

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“…Life Sci. Differential screening of cDNAs from tomato [157], Arabidopsis [158], rape [159], strawberry [160], barley [161], maize [162] and Chlorella protothecoides (S. Hö rtensteiner, unpublished) have led to the isolation of a number of different senescence-related genes [8]. 56,1999 Review Article 341 also resemble senescence.…”

Section: Significance Of Chl Breakdownmentioning

confidence: 99%

Chlorophyll breakdown in higher plants and algae

Hörtensteiner¹

1999

Cellular and Molecular Life Sciences (CMLS)

134

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Leaf senescence is accompanied by the metabolism of chlorophyll (Chl) to nonfluorescent catabolites (NCCs). The pathway of Chl degradation comprises several reactions and includes the occurrence of intermediary catabolites. After removal of phytol and the central Mg atom from Chl by chlorophyllase and Mg dechelatase, respectively, the porphyrin macrocycle of pheophorbide (Pheide) a is cleaved. This two-step reaction is catalyzed by Pheide a oxygenase and RCC reductase and yields a primary fluorescent catabolite (pFCC). After hydroxylation and additional species-specific modifications, FCCs are tautomerized nonenzymically to NCCs inside the vacuole. Different subcellular compartments participate in Chl catabolism and, thus, transport processes across membranes are required. This review focuses on the catabolites and the individual reactions of Chl breakdown in higher plants. In addition, the pathway is compared to Chl conversion to red catabolites in an alga, Chlorella protothecoides. Finally, the significance and regulation of Chl degradation are discussed.

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Section: Significance Of Chl Breakdownmentioning

confidence: 99%

Chlorophyll breakdown in higher plants and algae

Hörtensteiner¹

1999

Cellular and Molecular Life Sciences (CMLS)

134

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“…The loss in chlorophyll and decline in photosynthesis trigger leaf senescence (Smart 1994;Bleecker and Patterson 1997). Although leaf senescence is a degenerative process, it plays a vital role in nutrient recycling (Himelblau and Amasino 2001;Smart et al 1995). The released nutrients are transferred to actively growing young leaves and developing fruits and seeds (Gan 2007).…”

Section: Introductionmentioning

confidence: 99%

Effects of early-fruit removal on endogenous cytokinins and abscisic acid in relation to leaf senescence in cotton

et al. 2009

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Numerous studies have shown that early-fruit removal enhances vegetative growth and development of cotton (Gossypium hirsutum L.). However, few studies have examined changes in leaf senescence and endogenous hormones due to fruit removal. The objective of this study was to determine the correlation between some endogenous phytohormones, particularly the cytokinins and abscisic acid (ABA), and leaf senescence following fruit removal. Cotton was grown in pots and in the field during 2005 and 2006. Two early-fruiting branches were excised from plants at squaring to form the fruit removal treatment while the non-excised plants served as control. Plant biomass, seed cotton yield, cytokinins and ABA levels in main-stem leaves and xylem sap as well as main-stem leaf photosynthetic rate (Pn) and chlorophyll (Chl) concentration were determined after removal or at harvest. Fruit removals increased the leaf area, root and shoot dry weight and plant biomass at 35 days after removal (DAR), whether in potted or field-grown cotton; under field conditions, it also improved plant biomass and seed cotton yield at harvest. The Pn and Chl concentration in excised plants were significantly higher than in control plants from 5 to 35 DAR, suggesting that fruit removal considerably delayed leaf senescence. Fruit-excised plants contained more transzeatin and its riboside (t-Z ? t-ZR), dihydrozeatin and its riboside (DHZ ? DHZR), and isopentenyladenine and its riboside (iP ? iPA) but less ABA in both main-stem leaves and xylem sap than control plants from 5 to 35 DAR. These results suggest that removal of early fruiting branches delays main-stem leaf senescence, which can be attributed to increased cytokinin and/or reduced ABA. Cytokinin and ABA are involved in leaf senescence following early fruit removal.

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“…Plants grown on nutrient solution containing low S and low N showed fewer deficiency symptoms than plants grown on solutions containing low S and high N; this effect of mineral N availability was largely explained by differences in growth rate (Blake-Kalff et al , 1998). In spite of these observations, in oilseed rape, there have been few published studies to determine if the S remobilization observed in response to sulphate deficiency (i) is related to the enhancement of leaf senescence processes as classically observed in the case of mineral N deficiency (Smart et al , 1995; Gombert et al , 2006; Lim et al , 2007) and (ii) differs as a function of mineral N availability.…”

Section: Introductionmentioning

confidence: 99%

Remobilization of leaf S compounds and senescence in response to restricted sulphate supply during the vegetative stage of oilseed rape are affected by mineral N availability

Dubousset¹,

Abdallah²,

Desfeux³

et al. 2009

Journal of Experimental Botany

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The impact of sulphur limitation on the remobilization of endogenous S compounds during the rosette stage of oilseed rape, and the interactions with N availability on these processes, were examined using a long-term 34SO42− labelling method combined with a study of leaf senescence progression (using SAG12/Cab as a molecular indicator) and gene expression of the transporters, BnSultr4;1 and BnSultr4;2, involved in vacuolar sulphate efflux. After 51 d on hydroponic culture at 0.3 mM 34SO42− (1 atom% excess), the labelling was stopped and plants were subject for 28 d to High S-High N (HS-HN, control), Low S-High N (LS-HN) or Low S-Low N (LS-LN) conditions. Compared with the control, LS-HN plants showed delayed leaf senescence and, whilst the shoot growth and the foliar soluble protein amounts were not affected, S, 34S, and SO42− amounts in the old leaves declined rapidly and were associated with the up-regulation of BnSultr4;1. In LS-LN plants, shoot growth was reduced, leaf senescence was accelerated, and the rapid S mobilization in old leaves was accompanied by decreased 34S and SO42−, higher protein mobilization, and up-regulation of BnSultr4;2, but without any change of expression of BnSultr4;1. The data suggest that to sustain the S demand for growth under S restriction (i) vacuolar SO42− is specifically remobilized in LS-HN conditions without any acceleration of leaf senescence, (ii) SO42− mobilization is related to an up-regulation of BnSultr4;1 and/or BnSultr4;2 expression, and (iii) the relationship between sulphate mobilization and up-regulation of expression of BnSultr4 genes is specifically dependent on the N availability.

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The timing of maize leaf senescence and characterisation of senescence‐related cDNAs

Cited by 123 publications

References 35 publications

Chlorophyll breakdown in higher plants and algae

Chlorophyll breakdown in higher plants and algae

Effects of early-fruit removal on endogenous cytokinins and abscisic acid in relation to leaf senescence in cotton

Remobilization of leaf S compounds and senescence in response to restricted sulphate supply during the vegetative stage of oilseed rape are affected by mineral N availability

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