摘要:

The mechanisms controlling seed dormancy maintenance and release are not understood. To characterize the molecular events accompanying dormancy release, two‐dimensional gel electrophoresis was used to monitor changes in soluble proteins and in vitro translation products of embryonic mRNA populations during imbibition of dormant and nondormant (after‐ripened)Avena fatuaL. caryopses. No differences were observed between in vitro translation products of mRNA extracted from dry dormant and nondormant embryos. However, the expression patterns of several imbibition‐ and germination‐associated mRNAs were temporally modulated during the first 24 h of imbibition. Two dormancy‐associated mRNAs, represented by polypeptides D1and D2, were differentially overexpressed in dormant embryos after 3 h of imbibition. mRNA levels for D1and D2were about 8‐ and 3‐fold higher, respectively, in dormant embryos than in nondormant embryos after 3 h of imbibition. Overexpression of D1continued through 12 h of imbibition, while expression of both mRNAs fell to low and equivalent amounts in dormant and nondormant embryos after 24 h. Similar dormancy‐associated changes in two soluble proteins were observed during imbibition. The results demonstrate that steady‐state levels of specific mRNAs and proteins change during early imbibition of dormant and nondormantA. fatuaembryos and indicate that these changes may be associated with differential gene expression responsible for the mainte

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05490.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Low root‐zone temperatures (RZTs) are known to reduce soybean N2‐fixation. However, the relative sensitivity of the various stages of symbiosis establishment and function (N2‐fixation) to suboptimal RZTs is unresolved. We conducted experiments to examine the effect of exposure to a RZT of 15°C on nodulation. The control RZT was 25°C. Root temperatures were controlled by circulating cooled water around pots on a growth bench. Soybean seedlings [Glycine max(L.) Merr. cv. Maple Arrow] were inoculated with 1 ml of a log‐phase culture (approximately 10−8cells) ofBradyhizobium japonicumstrain 532C. They were then (1) maintained continuously at RZTs of 15 or 25°C, transferred to 15 or 25°C from the alternate temperature 7 days after inoculation (DAI), or transferred to 15 or 25°C at 14 DAI, and (2) maintained at 15 or 25°C, or transferred at either 1, 4 or 7 DAI. When seedlings were maintained at a RZT of 25°C nodule primordia (<1 mm) were visible at 7 DAI and N2‐fixation commenced at 14 DAI. Nodule function (N2‐fixation) appeared to be relatively insensitive to low RZTs since exposure of plants to 15°C following the onset of N2‐fixation (14 DAI) resulted in 68% of the N fixed and 78% of the dry weight of the 25°C RZT, although N partitioning to shoot tissues was reduced. In contrast, exposure to the low RZT shortly after inoculation declayed the onset of N2‐fixation for 4 to 6 weeks, primarily by inhibiting the early stages of nodulation. This resulted in fixed N and dry weight levels of 9% and 22%

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05491.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Nonstructural carbohydrates were determined in both embryo and endosperm of dormant (nongerminating) and afterripened (germinating) intact caryopses of wild oat (Avena fatuaL.). No changes in endosperm starch or soluble sugar were observed at the onset of germination (18 h). No changes in glucose, fructose, sucrose or starch within dormant or afterripened embryos correlated with onset of visual germination. In afterripened embryos, depletion of raffinose (18 h), stachyose (18 h) and galactose (24 h) was correlated with germination. In contrast, raffinose‐family oligosaccharide levels in dormant embryos remained constant for 7 days following imbibition. Germination of isolated dormant embryos on 88 mMgalactose‐containing media was accompanied by decreased endogenous levels of raffinose and stachyose. Isolated embryos from dormant caryopses incorporated14C from14C‐fructose into both raffinose and stachyose during 24 h of imbibition. In contrast, no14C incorporation into stachyose was observed in embryos from afterripened caryopses. No14C incorporation into raffinose was observed at 18 and 24 h. When in vitro activities of α galactosidase were measured, no temporal differences between dormant or afterripened caryopses were detected in either embryo or endosperm tissue. Although the mechanism associated with differences in utilization of raffinose and stachyose is yet unidentified, alterations in raffinose‐family oligosaccharide metabolism in the embryo appear to be a unique prerequisite for afterripening‐induced g

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05492.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

In situ location of phytoene desaturase, a key enzyme in the carotenoid biosynthesis pathway, has been investigated in chloroplasts from higher plants. For this purpose, an antiserum has been raised against the phytoene desaturase from the cyanobacteriumSynechococcusPCC 7942 overexpressed inE. coli. The specifity of this antiserum was demonstrated by inhibition of the enzymatic desaturation reaction in vitro. The antiserum was further purified and immunoabsorbed withE. coliproteins. The resulting IgG‐fraction was tested by western blotting against membrane proteins from chloroplasts of tobacco (Nicotiana tabacumL. cv. Samsun) and spinach (Spinacia oleraceaL. cv. Atlanta). Apparent molecular masses of immunoreactive proteins were 62 and 64 kDa. A western blot of different membrane fractions of spinach chloroplasts (inner and outer envelopes, and thylakoids) indicated a localization of the phytoene desaturase in thylakoids. A post embedding immunogold microscopy procedure was employed. In these experiments the main labelling (79%) was associated with thylakoid membranes of tobacco chloroplasts. Of the counted colloidal gold particles, 16% were found in the stroma. Only 5% were detected in the envelope membranes. These results give clear evidence that at least the majority of phytoene desaturase molecules is localized within thylakoid membranes of higher plant chloroplasts and that the presence of the enzyme in the envelope is of minor significanc

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05493.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Treatment with sucrose induced anthocyanin synthesis and phenylalanine ammonialyase (PAL, EC 4. 3. 1. 5) activity in leaf disks of Indian almond (Terminalia catappaL. Duthie). Co2+, an inhibitor of ethylene biosynthesis, inhibited anthocyanin synthesis and PAL activity when given together with sucrose. Ethephon (an exogenous source of ethylene) given along with sucrose, promoted anthocyanin synthesis and PAL activity, but in the presence of Co2+its effectiveness decreased. In an attempt to understand the inhibitory action of Co2+in the presence of ethephon, the effect of Co2+on PAL activity was studied in vitro. A kinetic study showed an uncompetitive type of inhibition of PAL by Co2+, which was not time dependent. Addition of 2‐mercaptoethanol, cysteine or glutathione overcame the in vitro effect of Co2+, and 2‐mercaptoethanol also restored the activity of PAL extracted from Co2+‐treated leaf disks. It is suggested that sulfhydryl group(s) might be involved in the inactivation of PAL by Co2+. The effects of N‐ethylmaleimide (NEM) and HgCl2(other sulfhydryl reagents) were also studied. Both NEM and Hg2+competitively inhibited PAL activity in vitro, and the inhibition could be reversed by sulfhydryl co

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05494.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

In cut carnations (Dianthus caryophyllusL. cv. Cally). petal senescence was associated with a climacteric pattern in ethylene production and an increase in ethylene sensitivity during the preclimacteric stage. The increase in ethylene sensitivity was caused by short‐chain saturated fatty acids (C7to C10) produced in the petals during the early stages of senescence. Pollination or application of octanoic acid to the styles of unpollinated flowers resulted in a sudden increase in ethylene sensitivity and a marked acceleration of senescence. Treatment with silver thiosulfate (STS) resulted in a suppression of ethylene sensitivity and a marked reduction in the levels of these fatty acids. However, even in STS‐treated flowers pollination or treatment with octanoic acid gave rise to a drastic increase in ethylene sensitivity. Exposure of carnation flowers to 2. 5‐norbornadicne (NBD) vapours resulted in a dramatic suppression of ethylene sensitivity which was also overridden by stylar application of octanoic acid. Exposure to NBD suppressed the increase in ethylene sensitivity caused by treatment with octanoic acid. It appears that short‐chain saturated fatty acids increased ethylene sensitivity by increasing the ability of the tissue to bind e

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05495.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

WhenPetunia hybridaL. cv. Rosy Morn Fertile suspension cells were inoculated in fresh medium with chloramphenicol (CAP), the activity of cytochrome C oxidase (EC 1. 9. 3. 1), and the respiration via the cytochrome pathway of isolated mitochondria decreased, while in untreated cells these parameters more than doubled in 2–3 days. However, the in vivo respiratory activity of the cytochrome pathway of CAP‐treated cells showed a similar course in time as that of untreated cells, even in the presence of an uncoupler, a large rise during the first 2–3 days followed by a decline. This leads to the conclusion that the respiration via the cytochrome pathway, even when measured in the presence of an uncoupler, is not the capacity of this pathway. Furthermore, the results suggest that, although new‐synthesis of proteins occurs directly after in‐oculation, a large overcapacity must be present of cytochrome pathway elements (at least of those that are mitochondrial encoded). CAP had little effect on the uninhibited respiration and the cyanide‐resistant, alternative pathway of thePetuniacells. However, the engagement of the alternative pathway (in the presence or absence of uncoupler) was increased in CAP‐treated cells, especially after day 3 of the batch cycle, possibly as an effect of higher sugar degradation in combination with substrate phosphorylation to compensate the loss of ATP‐synthesizing ability of the cytochrome pathway. It will be discussed that in general one should be careful using the term ‘capacity’ for the r

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05496.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

Protoplasts prepared from cultured albinoid cells of petunia do not express photosynthetic genes, such as those coding for chlorophylla/b‐binding (Cab) proteins or ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco). They therefore provide a convenient system for expressing recombinant photosynthetic genes, without background interference. Transfection of petunia protoplasts with vectors bearing theLhcbl*1Cabgene under the control of the 35S promoter of cauliflower mosaic virus (CaMV) resulted in the appearance of significant amounts of the specific transcripts, but not of the corresponding polypeptides, as inferred from northern and western blot analysis, respectively. The use of an expression vector carrying the translational enhancer Ω of tobacco mosaic virus (TMV) strongly enhanced the appearance of transfected gene products: western blot analysis of transfected protoplasts clearly revealed the appearance ofLemna gibbaLhcbl*1 and Lhcb2*1, tomato Lhcb2*1 and psaD, and pea rbcS gene products. Molecular weight estimations of the newly synthesized polypeptides indicated that each was promptly processed into its mature‐cleaved form within the transfected albinoid protoplasts. This occurred despite a lack of chlorophyll and the absence of a thylakoid

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05497.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A senescence‐specific protease has been purified from senescent unpollinated ovaries ofPisum sativumL. cv. Alaska by acidic extraction. (NH4)2SO4fractionation, ion exchange chromatography on CM‐Sephadex, and affinity chromatography on ribulose‐1,5‐bisphosphate carboxylase/oxygenase (Rubisco)‐Sepharose. Characterization of the purified protease indicated that it is a thiol‐endoprotease (EC 3. 4. 22 class) active over a wide pH range. Purified antibodies against this protease inhibit the degradation of Rubisco in autodigested extracts of senescent ovaries, suggesting that Rubisco might be a substrate for the protease in senescent pea ovaries. The relative levels of the protease were determined by an enzyme‐linked immunosorbent assay (ELISA) along the processes of ovary senescence and gibberellic acid (GA)‐induced fruit development, indicating its induction at the beginning of senescence and the suppression of its synthesis

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05498.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY

摘要:

A thiol‐endoprotease induced during the senescence of unpollinated ovaries ofPisum sativumL. cv. Alaska has been localized at both cellular and subcellular levels using purified antibodies. Immunoblot analysis showed a single band of 30 kDa in extracts from senescent ovaries 3 and 4 days post‐anthesis. Immunolocalization showed the accumulation of the protease within the exocarp and in the outer cell layers of the mesocarp of the senescent ovaries, although with an asymmetric distribution as illustrated in transverse sections. Ultrastructural localization indicates that the protease is associated with the tonoplast and with electron dense materials within the vacuole, where lysis of cell components occurs in senescent ovar

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1993.tb05499.x

出版商:Blackwell Publishing Ltd    

年代:1993

数据来源: WILEY