Fig. 7: Mitochondrial stress-induced mitophagy is inhibited in the trb1/trb2 mutants.

a Transgenic Arabidopsis expressing GFP-TRB1 and VAP27-1-RFP were treated with Conc A. The majority of TRB1-labelled mitochondria are found in contact with VAP27-labelled ER membrane inside the vacuole, suggesting that these two structures are internalised together. b High magnification images of (a). c, d Arabidopsis plants (Col-0; trb1/trb2; vap27-1,3,4,6) stably expressing Mito-mCherry were treated with DNP and Conc A to study the activity of mitophagy. Under non-stressed conditions, the mitochondrial turnover rate is similar in all plants analyzed. However, the number of vacuole-accumulated mitochondria is significantly reduced in both the trb1/trb2 and the vap27-1,3,4,6 (two independent lines, A1 and B2) mutants treated with DNP, suggesting that an interruption of ER-Mitochondrial interaction affects mitochondrial turnover following mitochondrial stress/mitochondrial damage. e, f The recovery of Arabidopsis seedlings after 4 h of DNP treatment was studied. The root growth of the trb1/trb2 mutant plants is significantly reduced compared to that in the wild type, suggesting that the DNP induced mitochondrial dysfunction has more impact on plant development when the function of TRB1 and TRB2 is impaired. The change of root length before and after recovery was measured, denoted as Δlength. n = 20 cells examined over three independent experiments for confocal quantification; n = 90 independent plants for root analysis; error bars are SEM, * 0.01 < P < 0.05, ** 0.001 < P < 0.01, *** P < 0.001 in two-way ANOVA, Sidak’s multiple comparisons test in d and Dunnett’s multiple comparisons test in f (scale bar = 10 μm for confocal; Scale bar = 200 nm for TEM; scale bar = 15 mm for root analysis).