Cytochrome b(6)f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis

Munekage, Y Takeda, S Endo, T Jahns, P Hashimoto, T Shikanai, T

Y. Munekage et al., Cytochrome b(6)f mutation specifically affects thermal dissipation of absorbed light energy in Arabidopsis, PLANT J, 28(3), 2001, pp. 351-359

40

INGLESE

Article

Plant Sciences","Animal & Plant Sciences

PLANT JOURNAL

0960-7412 → ACNP

28

3

2001

351 - 359

ISI

0960-7412(200111)28:3<351:CBMSAT>2.0.ZU;2-5

Light-induced lumenal acidification controls the efficiency of light harves ting by inducing thermal dissipation of excess absorbed light energy in pho tosystem II. We isolated an Arabidopsis mutant, pgr1 (proton gradient regul ation), entirely lacking thermal dissipation, which was observed as little nonphotochemical quenching of chlorophyll fluorescence. Map-based cloning s howed that pgr1 had a point mutation in petC encoding the Rieske subunit of the cytochrome b(6)f complex. Although the electron transport rate was not affected at low light intensity, it was significantly restricted at high l ight intensity in pgr1, indicating that the lumenal acidification was not s ufficient to induce thermal dissipation. This view was supported by (i) slo w de-epoxidation of violaXanthin, which is closely related to lumenal acidi fication, and (ii) reduced 9-aminoacridine fluorescence quenching. Although lumenal acidification was insufficient to induce thermal dissipation, grow th rate was not affected under low light growth conditions in pgr1. These r esults suggest that thermal dissipation is precisely regulated by lumenal p H to maintain maximum photosynthetic activity. We showed that pgr1 was sens itive to changes in light conditions, demonstrating that maximum activity o f the cytochrome b(6)f complex is indispensable for short-term acclimation.