Abstract
BackgroundTubby-like proteins (TLPs), characterized by a signature tubby domain, are widespread in plants and animals. To date, only plant TLPs involved in multifarious stress responses and male gametophyte development have been identified. However, studies on the molecular functions of plant TLPs are largely unknown.ResultsIn this investigation, the roles of a TLP from Malus domestica (MdTLP7) in response to abiotic stresses were characterized by expressing it in Arabidopsis. The expression of wild-type full-length MdTLP7 (FL) significantly increased the stress tolerance of Arabidopsis seedlings to osmotic, salt, cold and heat stress, while the expression of truncated MdTLP7 containing only the tubby domain (Tub) also showed some function. Located on a central α helix surrounded by 12 anti-parallel β strands in the tubby domain, the K190/R192 site may be involved in fixation to the plasma membrane, as shown by 3D homology modelling with animal TLPs. This site might play a crucial role in anti-stress functions since site-directed mutagenesis of MdTLP7 reduced stress tolerance. Subcellular localization showed that MdTLP7 was mainly localized in the plasma membrane in plant cells, suggesting that it might participate in the transduction of stress signals.ConclusionsThe results of this study showed that MdTLP7 could improve abiotic stress tolerance not only in bacteria but also in plants. The K190/R192 residues in the tubby domain were not only the plasma membrane binding site of MdTLP7 but also played a key role in stress tolerance. These results may provide a basis for further exploring the mechanism of anti-stress functioning and downstream target genes of plant TLPs.
Highlights
Tubby-like proteins (TLPs), characterized by a signature tubby domain, are widespread in plants and animals
Expression of MdTLP7 enhanced abiotic stress tolerance in Arabidopsis To examine the function of MdTLP7 in the plant stress response, the full-length cDNAs of wild-type full-length MdTLP7 (FL) and truncated MdTLP7 with only the tubby domain (Tub) were transformed into wild-type Arabidopsis (WT) by the CaMV 35S promoter
The results suggested that the expression of wild-type MdTLP7 (FL) or truncated MdTLP7 (Tub) enhanced tolerance to osmotic and salt stresses
Summary
Tubby-like proteins (TLPs), characterized by a signature tubby domain, are widespread in plants and animals. Only plant TLPs involved in multifarious stress responses and male gametophyte development have been identified. Studies on the molecular functions of plant TLPs are largely unknown. The tubby-like proteins (TLPs) are widely distributed in the animal and plant kingdoms. Many cellular functions of TLPs are involved in vesicular trafficking, the mediation of insulin signalling, gene transcription, G-protein signalling, and ribosomal RNA synthesis [5,6,7,8,9]. Several TLPs in plants have been identified, their roles are elusive. Several plant TLPs are upregulated under abiotic and biotic stress [4, 10,11,12,13]
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