Table 2.
Kinetics of qM dark relaxation in npq4 leaves. The kinetic components qM and qI were deconvolved from dark recovery of NPQ in npq4 leaves. Dark-adapted leaves were exposed to white actinic light for 60 min at 400 µmol photons m−2 s−1, RT, following 60 min of dark recovery. (upper section) Before NPQ induction, leaves were vacuum-infiltrated with 150 mM sorbitol and either 50 µM nigericin (uncoupler, collapsed the ΔpH across the thylakoid membranes), 2 µM myxothiazol (respiratory chain inhibitor) or 100 µM lincomycin (chloroplast protein biosynthesis inhibitor). (middle section) The kinetic components qM and qI were measured in npq4 double mutants lacking zeaxanthin (npq4npq1) or lacking lutein (npq4lut2). (lower section) Components qM and qI were measured in npq4 double mutants depleted of Lhcb subunits CP26 and CP24 (npq4koLhcb5/6), CP29 and CP24 (npq4koLhcb4/6), lack the entire LHC (npq4ch1), or unable to activate state transition (npq4stn7) or chloroplast avoidance movement (npq4phot2). Each dataset was fitted with an exponential function NPQ = AqI + AqM e(−t/τqM) and the kinetics of qM relaxation were assessed in the different samples by comparing amplitudes of parameters A. Significantly different values (Student's t-test) with respect to WT are marked with asterisks.
| τqM (min) | AqM | AqI | |
|---|---|---|---|
| npq4 | 28.4 ± 4.5 | 0.63 ± 0.03 | 0.35 ± 0.03 |
| npq4 + nigericin | — | — | 0.90 ± 0.03* |
| npq4 + myxothiazol | 34.7 ± 13.9 | 0.52 ± 0.08 | 0.40 ± 0.09 |
| npq4 + lincomycin | 37.3 ± 6.3 | 0.58 ± 0.04 | 0.39 ± 0.04 |
| npq4npq1 | 15.7 ± 1.3* | 0.56 ± 0.02 | 0.34 ± 0.01 |
| npq4lut2 | 27.7 ± 3.1 | 0.80 ± 0.03* | 0.33 ± 0.03 |
| npq4koLhcb5/6 | 22.8 ± 3.4 | 0.49 ± 0.03 | 0.28 ± 0.03 |
| npq4koLhcb4/6 | 20.7 ± 3.5 | 0.49 ± 0.03 | 0.29 ± 0.03 |
| npq4ch1 | 14.3 ± 1.2* | 0.71 ± 0.03* | 0.11 ± 0.03* |
| npq4stn7 | 14.2 ± 1.9* | 0.55 ± 0.04 | 0.37 ± 0.06 |
| npq4phot2 | 15.3 ± 5.8* | 0.28 ± 0.05* | 0.27 ± 0.09* |