摘要:

The relationship between the size of the light harvesting antenna to photosystem II (LHCII) and quenching of non‐photochemical and dark level fluorescence was studied in wild‐type rye (Secale cerealeL. cv. Musketeer) and barley (Hordeum vulgareL. cv. Gunilla) as well as in the barley chlorophyllb‐lesschlorinaF2 mutant (H. vulgareL. cv. Dornaria,chlorina‐F2). Exposure for 10 min to an irradiance of 500 μmol m−2s−1resulted in a strong (0.71–0.73) non‐photochemical (qs) quenching of the fluorescence yield in wild‐type (WT) material, while the barleychlorinaF2‐mutant was quenched to 75% of this level. Relaxation of qsin darkness revealed a fast initial decay, related to relaxation of the high‐energy‐state dependent (qE) part of qs. Etiolated seedlings of rye and barley exposed to intermittent light (IML) for 36 cycles of 2 min light and 118 min darkness had suppressed Chlband LHCII‐production in both WT rye and barley, while the barleychlorinaF2‐mutant became totally devoid of all LHCII‐polypeptides. It was found that the levels of qsand qswere similar in control grown barleychlorinaF2 and IML‐grown WT rye and barley, but qswas reduced by 30 to 35% and qsby 50 to 65%, respectively, as compared to control‐grown. WT plants. No significant qscould be detected in IML‐grown barleychlorinaF2. It is clear, from these changes in in vivo fluorescence quenching in rye and barley that a significant level of qsis detectable even in the absence of LHCII. Only when the proximal antennae are totally absent, does qEcompletely disappear. We conclude that the presence of LHCII is not an absolute requirement for qE‐quenching and suggest that distal as well as proxim

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02987.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

We have examined the growth and gravitropic response of seedling roots of rapeseed (Brassica napus. CrGC5–1) transformed byAgrobacterium rhizogenesA4, in order to evaluate if this could constitute a new model system for the study of gravitropism. The transformed clone chosen for study had integrated full‐length TL‐ and TR‐DNA from pRi (the root inducing plasmid), and thus included all of the agrobacterial genes potentially involved in the modified phenotype of transformed plants. In the vertical position, the growth rate of transformed roots was higher than controls. During 24 h of continuous stimulation, the optimal angle for gravitropic bending in normal roots was 135° (with respect to the gravity axis), with decreasing response at 90° and 45°. For transformed roots, slight curvature developed at 45° and at 90°, and stronger curvature was observed at 135°, though transformed roots tips never reached the vertical position. The minimum stimulation time necessary to elicit a response (presentation time) was also determined: it was signficantly shorter in normal roots (80 s) than in transformed ones (120 s). The results show that pRi transformed roots are less sensitive to gravity than

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02988.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The CD3 mutant of wheat is a chlorophyll(Chlo‐deficient mutant the phenotype of which depends upon the accumulation of the light‐harvesting Chla/bprotein complex in leaves in response to the intensity of illumination. In the present studies, the rates of synthesis and/or uptake, and degradation of the light‐harvesting Chl apoprotein in chloroplasts of wild‐type wheat (Triticum aestivumL. selection ND 496) and CD3 wheat leaf segments were examined in response to two different intensities of illumination. We were interested particularly in the 21. 23 kDa proteins of the light‐harvesting Chla/bcomplex of photosystem I (LHCI) and the 25. 27. 29 kDa proteins of the light‐harvesting Chla/bcomplex of photosystem II (LHCII). The accumulation of [35S]‐Met into the light‐harvesting Chl protein of CD3 wheat chloroplasts was impaired by a high but not by a low light fluence. The levels of radiolabel in the supernatant fractions of leaf tissue homogenates from the wild‐type and CD3 wheats were not significantly different over time, suggesting that the cellular uptake of [35S]‐Met was not limiting in the mutant. The high fluence did not enhance the degradation of light‐harvesting Chl protein from CD3 wheat thylakoids. Our data indicate an impairment in the light‐harvesting Chl protein synthesis/membrane uptake system in CD3 wheat leaves under high fluence. A recovery in levels of the inner LHCPII, but not of LHCPI, was observed in the Chl‐deficient wheat mutant after a prolonged (4 days) exposure to high fluence. Under low fluence, LHCP was added to both photosystem II (PSH) and photosystem I (PSI) but only that added to PSI remained in thylakoids after seedlings were

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02989.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Treatment of tobacco suspension cells (Nicotiana tabacumcv. KY 14) with a purifiedβ‐1,4‐endoxylanase fromTrichoderma viride[1 μg enzyme (ml cells)−1] caused a 13‐fold increase in the levels of acylated sterol glycosides and elicited the synthesis of phytoalexins. A commercial preparation of xylanase fromTrichoderma viridecaused an identical shift in sterols. In contrast, a commerical xylanase fromAureobasidium pullaulanshad no effect on the levels of acylated sterol glycosides, but did elevate the levels of sterol esters. Treatment of the cells with Cu2+or Ag+also evoked a severalfold increase in the levels of acylated sterol glycosides. Analysis of the various sterol lipid classes revealed that the large xylanase‐induced increase in acylated sterol glycosides occurred at the expense of sterol esters, free sterols and sterol glycosides. Further analyses revealed that the most abundant phytosterol in each of the four classes of sterol lipids wasβ‐sitosterol. Linoleic acid was the most abundant fatty acid in the sterol esters, and palmitic and linoleic acids were the most abundant fatty acids in the acylated sterol glycosides. Glucose was the only sugar moiety in the sterol glycoside and acvlated sterol glycosides. Glucose was the only sugar moiety in the sterol glycoside and acylated sterol glycoside fractions. The results of the present study demonstrate that xylanase fromTrichoderma virideinduces a dramatic shift in the level of acylated sterol glycosides, indicating that endoxylanase was probably the active component in the cellulase enzyme preparations used in our

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02990.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The rates of phosphate uptake and photosynthesis were simultaneously determined in order to investigate the relationship between phosphate use and photosynthesis.Porphyra umbilicalis(L.) Kützing exhibited two different phosphate uptake kinetics. The first one followed a saturation model and was observed in light (maximum phosphate uptake rate. Vmax= 94 ± 30 nmol P1m−2s−1: semisaturation constant. S15= 4.0 ± 3.4 μM: phosphate compensation point. PCP = 0.3 ± 0.4 μMγ: the seeraid one was linear and worked at high external phosphate concentrations in the dark. Inhibition of photosynthesis by removing the inorganic carbon from the medium produced the same effect aa darkness on phosphate uptake. Successive bicarbonate additions produced increments of photosynthesis rate and the recovering of the phosphate uptake pattern observed in light. The results showed thatPorphyra umbilicalis, at the typical phosphate concentrations in its natural habitat, takes up phosphate in the light through the operation of a photosynthetically controlled act

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02991.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

Enolase was purified from maze (Zea maysL. inbred B73)seeds to a 55 and 56 kDa protein doublet based upon sodium dodecyl sulfate – polyacrylamide gel electrophoresis. Purification included ammonium sulfate‐precipitation, gel filtration, Mono Q, and Phenyl Superose chromatography. Two‐dimensional gels further resolved the 56 kDa protein into three isoselectric forms. Polyclonal antibodies raised against the purified proteins, were found to bind specifically to both the 55 and 56 kDa proteins during purification. Theses antibodies did not recognized a 56 kDa protein when the strain was complemented with maize enolase (pZM245). Maize enolase antibodies recognized a extracts indicated that the 55 kDa form of enolase was more abundant in roots. Enolase protein levels remained unchanged in maize roots after 24 h of anaerobiosis, even though the specific activity of enolase increased to twice its initial levels. A plastid form of enolase in maize could not be found as either enolase activity or protein (with immunob

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02992.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effects of paclobutrazol treatment on plasma membrane lipid composition and ATPase activity of bell pepper fruit (Capsicum annuum) subjected to chilling temperatures were assessed. Application of the growth regulator paclobutrazol affected plant growth and fruit morphology. The plants were more compact and the fruits were less elongated than control fruits. There was about 60% more plasma membrane on a fresh weight basis from treated fruits. At harvest there was no difference in sterol to phospholipid ratio, or in phospholipid fatty acid composition of control compared with paclobutrazol treated fruit. However, plasma membrane ATPase acitivity of treated fruit was two times higher than that of control fruit. After storage at chilling temperature (2°C), the control fruit developed more chilling iniury, and had greater weight loss and a higher rate of K+leakage than paclobulrazol treated fruit. Plasma membrane phospholipid content decreased and saturation of phospholipid fatty acids was higher than in control fruit. These two changes were largely absent in plasma membrane from treated fruit. At harvest antioxidant levels in the plasma membrane of paclobutrazol treated peppers were higher than in those of controls and changed little during storage, whereas levels in control fruit plasma membrane decreased 66%. ATPase activity increased and then decreased in control fruit held at low temperature, whereas in treated fruit activity was constant. The protective effect of paclobutrazol against chilling injury of pepper fruit may result from a combination of its effect on fruit morphology, and protection of the lipids against oxidative stress

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02993.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

A spectrophotometric assay was devised to characterize the asparaginyl (Asn) endopeptidase activity from the endosperm of castor oil seeds. (Ricinus communisL. var. Baker 296). The assay measures the release ofp‐nitroaniline from the hydrolysis of benzoyl‐l‐Asn‐p‐nitroanilide. Assay sensitivity was improved through diazotization of the reaction product withN(]‐napthy])‐ethylenediamine dihydrochloride: diazotizedp‐nitroaniline was determined spectrophotometrically at 548 nm (ɛ548= 1.64 × 10−1M−1cm−2). By using this assay. Asn endopeptidase activity was detected in endosperm extracts of developing, mature and germinating castor seeds. Comparison of the Asn endopeptidase activities of developing and germinating castor endosperms revealed that they: 1) have identical pH‐activity profiles with optimal activity occuring at pH 5.4: 2) are heat‐labile proteins displaying comparable thermal stability profiles, and 3) are activated and inhibited by dithiothreitol and thiol modifying reagents, respectively. Thus, the Asn endopeptidases of developing and germinating castor seeds are very similar, if not identical, cysteine proteases. The most significant increase in the activity of endosperm Asn endopeptidase occurs during the full coryledon to maturation stage of seed development, this period coincides with the most active phase of reserve protein accumulation by ripening castor oil seeds. Asn endopeptidase activity of fully mature (dry) castor seeds was about 2‐fold lower than that of muturation stage ripening castor oil seed. Asn endopeptidase activity showed a slight reduction over the inicial 2‐day period following seed imbibition, and then rapidly decreased over the next several days of germination. The results are compatible with the proposal that Asn endopeptidase functions both to process storage preproteins following their import into protein bodies of developing seeds, as well as to participate in the mobilization of storage proteins during the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02994.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The response of 10‐day‐old seedlings ofRaphanus sativusL. cv. Fakir to salt stress (100 mMto 200 mMNaCl) was investigated. Three weeks after initiation of salt treatment, the fresh weight of the shoots of salt‐treated plants was half that of untreated plants. The salt stress resulted in the accumulation of Na+, preferably in the old leaves. The K+level was reduced by as much as 50% in the old leaves of NaCl‐treated plants, whereas this reduction was only 20–25% in the young leaves. Free proline accumulated in all aerial organs, and the highest levels were found in the young leaves. Patterns of total proteins extracted from the leaves of control or salt‐treated plants were compared. The most obvious change concerned a 22‐kDa, pl 7.5 polypeptide, which accumulated after exposure of the plants to NaCl. The appearance of this polypeptide was also mediated by a rapid drought stress, and sequencing indicated that it is related to the Künitz protease inhibitor family. A cDNA clone corresponding to the radish 22‐kDa polypeptide was obtained and sequenced. Northern blot analysis showed that salt stress induces a large accumulation of this mRNA in the

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02995.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY

摘要:

The effect of exogenous ABA on acquisition of desiccation tolerance has been well documented for the embryos of several species. including maize (Zea maysL.). It has also been suggested that endogenous ABA plays a role in regulating the same phenomena. To test this hypothesis, endogenous ABA was quantified by radioimmunoassay. Our results show that: (1) during embryogenesis in maize, endogenous ABA increase‐concomitantly with the acquisition of desiccation tolerance: (2) ABA deficient embryos of thevp5 mutant are desiccation intolerant, but tolerance can he induced by exogenous ABA: and (3) desiccation tolerance is acquired if desiccation sensitive embryos undergo a slow drying treatment, during which ABA increases. However, when embryos were preincubated in fluridone to prevent ABA accumulation during slow drying, desiccation tolerance was induced in spite of the low level of endogenous ABA in the embryo. Our results cast doubts on an exclusive role of ABA in the acquisition of desiccation tolerance in maize embry

ISSN:0031-9317    

DOI:10.1111/j.1399-3054.1994.tb02996.x

出版商:Blackwell Publishing Ltd    

年代:1994

数据来源: WILEY