The Arabidopsis sn-1-specific mitochondrial acylhydrolase AtDLAH is positively correlated with seed viability

Abstract

Lipid-derived molecules produced by acylhydrolases play important roles in the regulation of diverse cellular functions in plants. In Arabidopsis, the DAD1-like phospholipase A1 family consists of 12 members, all of which possess a lipase 3 domain. In this study, the biochemical and cellular functions of AtDLAH, an Arabidopsis thaliana DAD1-like acylhydrolase, were examined. Bacterially expressed AtDLAH contained phospholipase A1 activity for catalysing the hydrolysis of phospholipids at the sn-1 position. However, AtDLAH displayed an even stronger preference for 1-lysophosphatidylcholine, 1-monodiacylglycerol, and phosphatidic acid, suggesting that AtDLAH is a sn-1-specific acylhydrolase. The AtDLAH gene was highly expressed in young seedlings, and its encoded protein was exclusively localized to the mitochondria. AtDLAH-overexpressing transgenic seeds (35S:AtDLAH) were markedly tolerant to accelerated-ageing treatment and thus had higher germination percentages than wild-type seeds. In contrast, the atdlah loss-of-function knockout mutant seeds were hypersusceptible to accelerated-ageing conditions. The 35S:AtDLAH seeds, as opposed to the atdlah seeds, exhibited a dark red staining pattern following tetrazolium treatment under both normal and accelerated-ageing conditions, suggesting that AtDLAH expression is positively correlated with seed viability. The enhanced viability of 35S:AtDLAH seeds was accompanied by more densely populated epidermal cells, lower levels of accumulated lipid hydroperoxides, and higher levels of polar lipids as compared with wild-type and atdlah mutant seeds. These results suggest that AtDLAH, a mitochondrial-localized sn-1-specific acylhydrolase, plays an important role in Arabidopsis seed viability.

Regulatory‐associated protein of TOR (RAPTOR) alters the hormonal and metabolic composition of Arabidopsis seeds, controlling seed morphology, viability and germination potential

“…We obtained similar results for both data sets: whereas the WT reached a germination efficiency of 97%, the raptor1b seeds only achieved a germination efficiency of 80% (Figure ). Comparison of the germination success of freshly harvested seeds and seeds stored for 1 year, as well as seeds subjected to accelerated aging (Elias and Copeland, ; Sattler et al ., ; Seo et al ., ) or abiotic stresses (Figures S5 and S6), additionally underlined the finding that raptor1b seeds were not only less viable but were also less tolerant to dry storage and environmental perturbations. Although the observation of decreased stress tolerance is in full agreement with previous results obtained from TOR inhibition, where salt and osmotic stresses led to decreased activity of ribosomal S6 kinase, a downstream target of TOR (Mahfouz et al ., ), or increased sensitivity to osmotic stress (Deprost et al ., ).…”

Mitochondrial function modulates touch signalling in Arabidopsis thaliana

“… Interaction of touch response with energy and hormonal signalling pathways. The touch response of 26 marker genes selected from the five clusters (Figure ), in kin10 mutants: Sn RK 1 , Sucrose non‐fermenting Related protein Kinase 1; GA 2 OX 2 , gibberellin 2‐oxidase (Yamauchi et al ., ); DLAH , DAD 1‐like acylhydrolase (Seo et al ., ); EXL 1 , exordium‐like 1 (Schroder et al ., ); ILL 6 , IAA ‐leucine resistant ( ILR )‐like gene 6 (Widemann et al ., ); CML 38 , calmodulin‐like 38 (Lokdarshi et al ., ); DIC 1 , dicarboxylate carriers 1 (Palmieri et al ., ); JAZ 7 , jasmonate‐zim‐domain protein 7 (Yan et al ., ); ZAT 11 , zinc finger of Arabidopsis thaliana 11 (Liu et al ., ); GRP , glycine‐rich protein; AOC 1 , allene oxide cyclase 1 (Stenzel et al ., ); CML 41 , calmodulin‐like 41 (McCormack and Braam, ); NDB 2 , NAD (P)H dehydrogenase B2 (Elhafez et al ., ); SNARE , soluble N‐ethyl‐maleimide sensitive factor attachment protein receptors; ERF 6 , ethylene responsive element binding factor 6 (Moffat et al ., ); RRTF 1 , redox responsive transcription factor 1 (Matsuo and Oelmüller, ); PEARLI 4, phospholipase‐like protein; GLTP , Glycolipid transfer protein; PGIP 2 , polygalacturonase‐inhibiting protein 2 (Ferrari et al ., ); MES 5 , methyl esterase 5 (Yang et al ., ); NAC 090 , NAC domain containing protein 90; BTI 3 , VIRB 2‐interacting protein 3 (Hwang and Gelvin, ); TCH 4 , Touch 4 (Xu et al ., ); and ABA 1 , ABA DEFICIENT 1 (Assmann et al ., ). Statistical significance of values was determined by comparing to wild‐type using Student's t ‐test (* P < 0.05, ** P ≤ 0.01; n = 3).…”

Overexpression of the PP2A regulatory subunit Tap46 leads to enhanced plant growth through stimulation of the TOR signalling pathway

“…Tetrazolium uptake assays were performed to determine seed viability. Upon incubation with the tetrazolium solution, viable seeds are stained red, while seeds with low viability remain white ( Oge et al , 2008 ; Seo et al , 2011 ). OE-5 and OE-10 seeds survived and germinated at a higher frequency after 24 or 48 hours of treatment, compared with WT seeds ( Fig.…”