Pectin, one of the main components of plant cell wall, is deesterified in muro by PME (Pectin methylesterase). PME activity is particularly regulated by inhibitor proteins known as the pectin methylesterase inhibitor (PMEI). The PMEI plays a key role in wounding, osmotic stress, senescence and seed development. However, the role of PMEI in plant species still remains to be demonstrated especially in wheat. To facilitate the studies on the expression of the TaPMEI gene, RT-PCR was performed using leaf, stem and root tissues in response to exogeneous application of phytohormones and abiotic stress treatments. Transcription of the TaPMEI gene was significantly induced in NaCl, H2O2 and SA treatments, and reduced when plants were treated with ABA. To elucidate the subcellular localization of the TaPMEI protein, TaPMEI:GFP fusion construct was transformed into onion epidermal cells by particle bombardment. The fluorescence signal was exclusively detected in cell wall of the cells. In order to obtain recombinant TaPMEI protein, the TaPMEI protein, expressed in E.coli as a MBP (~42.5 kDa) fusion protein recombinant. Purification and functinal analysis of TaPMEI as an inhibitor of PME activity are described.

Most vacuolar proteins are synthesized on the endoplasmic reticulum (ER) as a proprotein precursor and then transported to vacuoles. In vacuoles, they are converted into the respective mature form. TaVPE1 and TaVPE2 were isolated from the cDNA library that was prepared from the wheat kernels at 16 and 18 days after fertilization (DAF). Additionally, putative TaVPEs (TaVPE3, TaVPE4) were isolated by inverse PCR (IPCR) using GrainGenes database. Each open reading frame (ORF) encodes 495, 497, 495, 456 amino acids, respectively. TaVPEs were closely related in respect to peptide comparisons and their sequence homologies were ranged from 84% to 93%. The TaVPE genes showed various expression patterns in response to exogenous treatment of phytohormones. The transcript of TaVPE1 was detected slightly and steadily after exposure to all phytohormones and the accumulation of TaVPE2 transcript was increased from 24 hours in NaCl treatment. The transcript of TaVPE3 was increased from 48 hours in response to H2O2 and decreased after exogenous application of ABA and salicylic acid. In case of TaVPE4, the transcript of TaVPE4 were weakly detected all time points of each phytohormone treatment.