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Comparative analysis of biochemical properties of mesophyll and bundle sheath chloroplasts from various subtypes of C4 plants grown at moderate irradiance

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Romanowska E., Drożak A.

2006

vol. 53

issue 4

709-719

The photochemical characteristics of mesophyll and bundle sheath chloroplasts isolated from the leaves of C4 species were investigated in Zea mays (NADP-ME type), Panicum miliaceum (NAD-ME type) and Panicum maximum (PEP-CK type) plants. The aim of this work was to gain information about selected photochemical properties of mesophyll and bundle sheath chloroplasts isolated from C4 plants grown in the same moderate light conditions. Enzymatic as well as mechanical methods were applied for the isolation of bundle sheath chloroplasts. In the case of Z. mays and P. maximum the enzymatic isolation resulted in the loss of some thylakoid polypeptides. It was found that the PSI and PSII activities of mesophyll and bundle sheath chloroplasts of all species studied differed significantly and the differences correlated with the composition of pigment-protein complexes, photophosphorylation efficiency and fluorescence emission characteristic of these chloroplasts. This is the first report showing differences in the photochemical activities between mesophyll chloroplasts of C4 subtypes. Our results also demonstrate that mesophyll and bundle sheath chloroplasts of C4 plants grown in identical light conditions differ significantly with respect to the activity of main thylakoid complexes, suggesting a role of factor(s) other than light in the development of photochemical activity in C4 subtypes.

High light induced accumulation of two isoforms of the CF1 α-subunit in mesophyll and bundle sheath chloroplasts of C4 plants

100%

Romanowska E., Powikrowska M., Zienkiewicz M., Drożak A., Pokorska B.

2008

vol. 55

issue 1

175-182

The effect of light irradiance on the amount of ATP synthase α-subunit in mesophyll (M) and bundle sheath (BS) chloroplasts of C4 species such as maize (Zea mays L., type NADP-ME), millet (Panicum miliaceum, type NAD-ME) and guinea grass (Panicum maximum, type PEP-CK) was investigated in plants grown under high, moderate and low light intensities equal to 800, 350 and 50 µmol photons m-2 s-1, respectively. The results demonstrate that α-subunit of ATP synthase in both M and BS chloroplasts is altered by light intensity, but differently in the investigated species. Moreover, we identified two isoforms of the CF1 α-subunit, called α and ά. The CF1 α-subunit was the major isoform and was present in all light conditions, whereas ά was the minor isoform in low light. A strong increase in the level of the ά-subunit in maize mesophyll and bundle sheath thylakoids was observed after 50 h of high light treatment. The α and ά-subunits from investigated C4 species displayed apparent molecular masses of 64 and 67 kDa, respectively, on SDS/PAGE. The presence of the ά-subunit of ATPase was confirmed in isolated CF1 complex, where it was recognized by antisera to the α-subunit. The N-terminal sequence of ά-subunit is nearly identical to that of α. Our results indicate that both isoforms coexist in M and BS chloroplasts during plant growth at all irradiances. We suggest the existence in M and BS chloroplasts of C4 plants of a mechanism(s) regulating the ATPase composition in response to light irradiance. Accumulation of the ά isoform may have a protective role under high light stress against over protonation of the thylakoid lumen and photooxidative damage of PSII.

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2 Acta Biochimica Polonica

1 2008

1 2006

2 Drożak A.

2 Romanowska E.

1 Pokorska B.

1 Powikrowska M.

1 Zienkiewicz M.

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Comparative analysis of biochemical properties of mesophyll and bundle sheath chloroplasts from various subtypes of C4 plants grown at moderate irradiance

High light induced accumulation of two isoforms of the CF1 α-subunit in mesophyll and bundle sheath chloroplasts of C4 plants