Low-temperature Conditioning of Garlic “Seed” Cloves Induces Differential Response in Sprouts Proteome

Low-temperature conditioning of garlic (Allium sativum L.) “seed” cloves at 5 °C for 5 weeks substitutes the initial climatic requirements of the crop and accelerates the development of the crop cycle. Also, reduces growth and plant weight as well as the crop yields and increases the synthesis of phenolic compounds and anthocyanins in the bulbs at harvest. Plant acclimation to low-temperature is associated with deep changes in proteome composition. Since proteins are directly involved in plant response to environmental conditions, proteomics studies can significantly contribute to unravel the possible relationships between protein abundance and low-temperature acclimation. Therefore, the aim of this work was to study the changes in the protein profiles of garlic “seed” cloves subjected to conditioning at low-temperature using proteomics approach. Two sets of garlic bulbs were used, one set was stored at room temperature (23 °C), and the other was conditioned at low temperature (5 °C) for 5 weeks. Three sets of 25 bulbs of each condition were separated and the cloves of medium size (5 – 6 g) were selected. Total soluble proteins were extracted from sprouts of cloves with an adapted method and separated by isoelectric focusing using 24 cm strips, pH 4-7 and second dimension was carried out on 13% SDS-PAGE gels. 2-DE gels were stained with Coomassie blue and digitalized images were analyzed using Melanie v7.0. Sixty-two protein spots showing statistically significant changes in abundance between treatments were analyzed by LC-ESI-MS/MS. 81% of the spots were identified by database search analysis using the Mascot search engine. According to Gene Ontology these proteins were grouped into nine different categories in function to the biological processes in which they are involved; cellular response to stress, carbohydrate binding, regulation of transcription, transport of macromolecules, protein folding, photosynthesis, carbohydrate metabolism, nucleotide metabolism, and miscellaneous. The results indicated significantly increased protein spots including RNA-binding protein, chaperone and S-adenosylmethionine synthetase. Significantly decreased protein in garlic sprouts spots subjected to cold conditioning, which include mannose-specific lectin, macrophage migration inhibitory factor, annexin D2-like and glutathione S-transferase. This is the first report that analyzes the garlic proteome modifications induced by low-temperature conditioning of the “seed” cloves.