Comparison of Photosynthetic Activities of Spinach Chloroplasts with Those of Corn Mesophyll and Corn Bundle Sheath Tissue

Hardt, Haim; Kok, Bessel

doi:10.1104/pp.62.1.59

Cited by 23 publications

(9 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The marked stimulation of photosynthesis which malate causes in isolated bundle sheath tissue is consistent with this view [3,5]. Although the extent of the deficiency in photosystem II has since been questioned [6,7], recent work with bundle sheath strands having photosynthesis rates equal to those of the parent tissue implied that photosynthetic Oa evolution (and uptake) with COz as the acceptor is limited and that the high ATP demand for COa fucation is largely met by cyclic photophosphorylation mediated by photosystem I rather than via noncyclic or pseudocyclic photophosphorylation [5]. Cyclic photophosphorylation requires activation by electron flow from a suitable reductanr, which establishes appropriate redox poise in the electron carriers.…”

Section: Introductionsupporting

confidence: 64%

Photosynthetic electron transport in the bundle sheath of maize

Leegood¹,

Crowther

Walker³

et al. 1981

FEBS Letters

View full text Add to dashboard Cite

Section: Introductionsupporting

confidence: 64%

Photosynthetic electron transport in the bundle sheath of maize

Leegood¹,

Crowther

Walker³

et al. 1981

FEBS Letters

View full text Add to dashboard Cite

“…The in situ photochemical activities of maize BS chloroplasts are quite comparable to the highest activities reported for isolated BS chloroplasts (9). Perhaps more importantly, this paper also describes experiments in which we have successfully detected an electron transport-dependent H+ uptake by isolated BS fragments.…”

supporting

confidence: 62%

“…The PSII activity using DMQ as oxidant averaged 300 ,ueq/hr mg Chl at 21 nearly an order of magnitude than those previously reported for the photoreduction of benzoquinone in isolated maize BS cells (19,28). They also exceed the rates reported for benzoquinone reduction in Digitaria BS cells (21), and approach the value of 660 ,ueq/hr-mg Chl which Hardt and Kok (9) reported recently for the photoreduction of oxidized p-phenylenediamine in isolated maize chloroplasts. The same is true of the rates we found for the whole chain reaction H20 --+MV (200-350 ,ieq/hr-mg Chl) and for the PSI reaction ascorbate/DAD -+ MV (400-700 ,ieq/hr mg Chl), if one considers that the PSI activity given by Hardt and Kok (1000 ,teq/hr-mg Chl) was apparently not corrected for the extra 02 consumption due to the oxidation of ascorbate by°2 -These PSI and PSII activities are approximately one-half of those normally found in isolated spinach chloroplasts.…”

Section: Discussionmentioning

confidence: 59%

Photosynthetic Electron Transport in Isolated Maize Bundle Sheath Cells

Walker¹,

Izawa²

1979

Plant Physiol.

View full text Add to dashboard Cite

Fragments of bundle sheath strands, free of mesophyll cells and showing a chlorophyll a/b ratio of 6.0 to 6.6 were prepared from Zea mays by a mechanical method. They were unable to photoreduce ferricyanide but were able to photoreduce the membrane-permeant 2,5-dimethylquinone at a rate of 250 to 420 microequivalents per hour per mg chlorophyll (ueq/hr.mg Chi) at 21 C. In the presence of the catalase inhibitor KCN We have attempted to reevaluate the in situ photochemical activities of chloroplasts in isolated maize BS fragments by carefully optimizing the reaction conditions. We used 2,5-dimethylquinone (DMQ) as the PSII electron acceptor, which is a membranepermeant oxidant and is by far the more stable and therefore more reliable as a PSII acceptor than is unsubstituted p-benzoquinone (24). MV, a standard PSI electron acceptor for chloroplast studies, tumed out to be useful also for isolated BS cells. This was not surprising, since MV is a widely used contact herbicide ("paraquat") and is known to penetrate the leaf tissue readily (see, e.g. 3).The in situ photochemical activities of maize BS chloroplasts are quite comparable to the highest activities reported for isolated BS chloroplasts (9). Perhaps more importantly, this paper also describes experiments in which we have successfully detected an electron transport-dependent H+ uptake by isolated BS fragments. Preparation of BS Fragments. BS fragments were isolated from secondary leaves taken from 2-to 4-week-old plants. All isolation procedures were performed at 0 to 4 C using ice-chilled media. Ten to 12 g (fresh weight) of leaves were cut transversely into Ito 2-cm segments. Two to 3 g of these segments were combined with 5 ml of the isolation medium that contained 0.5 M sucrose, 80 mM Tricine-NaOH buffer (pH 7.8), 5 mM MgCl2, 10 mm KCI, 0.2% BSA, and 0.1% PVP (PVP-40, Sigma). The leaf segments were then thoroughly macerated (4-5 min) using a pair of razor blades attached to an electric kitchen knife. This step removed most of the mesophyll cells and the epidermis from the tissue. The fragments were transferred to a beaker together with the medium and kept in suspension using a magnetic stirrer. The procedure was repeated until the entire 10 to 12 g of the original material was processed. The suspension was then filtered though two layers of Miracloth, and the tissue remaining on the cloth was briefly rinsed with distilled H20. The washed fragments were resuspended in 150 ml of the isolation medium and sheared in a Waring Blendor for 9 to 15 sec in 3-sec bursts at low speed. MATERIALS

show abstract

“…By contrast, fully differentiated BS thylakoids have little functional PSII and normal or increased PSI levels, whereas Cyt b 6 f and ATP synthase complexes are quite evenly distributed between BS and M thylakoids. As a consequence, BS thylakoids carry out mostly cyclic electron flow and have low rates of linear electron flow (Woo et al, 1970;Hardt and Kok, 1978;Schuster et al, 1985). After several conflicting reports on protein levels of PSII and LHCII (Schuster et al, 1985;Bassi and Simpson, 1986;Oswald et al, 1990), a subsequent study clarified both activity and protein accumulation levels of PSI and PSII complexes in BS and M thylakoids (Meierhoff and Westhoff, 1993).…”

Section: Met1 and The Psii Assembly Process In Dimorphic Chloroplastsmentioning

confidence: 99%

“…In maize (and other NADPH-ME C4-type plants), active PSII is highly enriched in M chloroplasts compared with BS chloroplasts and BS chloroplasts primarily carry out cyclic electron transport and have low rates of linear electron transport (Woo et al, 1970;Hardt and Kok, 1978;Schuster et al, 1985;Meierhoff and Westhoff, 1993;Majeran et al, 2008). In previous comparative quantitative proteome analyses of isolated M and BS chloroplast fractions of maize leaves, we identified an abundant chloroplast tricopeptide repeat (TPR) protein (GRMZM2G312910) that was 3-to 5-fold enriched in M chloroplasts compared with BS chloroplasts (Majeran et al, 2005;Friso et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

MET1 Is a Thylakoid-Associated TPR Protein Involved in Photosystem II Supercomplex Formation and Repair in Arabidopsis

et al. 2015

View full text Add to dashboard Cite

ORCID ID: 0000-0001-9536-0487 (K.J.v.W.)Photosystem II (PSII) requires constant disassembly and reassembly to accommodate replacement of the D1 protein. Here, we characterize Arabidopsis thaliana MET1, a PSII assembly factor with PDZ and TPR domains. The maize (Zea mays) MET1 homolog is enriched in mesophyll chloroplasts compared with bundle sheath chloroplasts, and MET1 mRNA and protein levels increase during leaf development concomitant with the thylakoid machinery. MET1 is conserved in C3 and C4 plants and green algae but is not found in prokaryotes. Arabidopsis MET1 is a peripheral thylakoid protein enriched in stroma lamellae and is also present in grana. Split-ubiquitin assays and coimmunoprecipitations showed interaction of MET1 with stromal loops of PSII core components CP43 and CP47. From native gels, we inferred that MET1 associates with PSII subcomplexes formed during the PSII repair cycle. When grown under fluctuating light intensities, the Arabidopsis MET1 null mutant (met1) showed conditional reduced growth, near complete blockage in PSII supercomplex formation, and concomitant increase of unassembled CP43. Growth of met1 in high light resulted in loss of PSII supercomplexes and accelerated D1 degradation. We propose that MET1 functions as a CP43/CP47 chaperone on the stromal side of the membrane during PSII assembly and repair. This function is consistent with the observed differential MET1 accumulation across dimorphic maize chloroplasts.

show abstract

Comparison of Photosynthetic Activities of Spinach Chloroplasts with Those of Corn Mesophyll and Corn Bundle Sheath Tissue

Cited by 23 publications

References 13 publications

Photosynthetic electron transport in the bundle sheath of maize

Photosynthetic electron transport in the bundle sheath of maize

Photosynthetic Electron Transport in Isolated Maize Bundle Sheath Cells

MET1 Is a Thylakoid-Associated TPR Protein Involved in Photosystem II Supercomplex Formation and Repair in Arabidopsis

Contact Info

Product

Resources

About