Proteome evolution of wheat (Triticum aestivum L.) aleurone layer at fifteen stages of grain development

The aleurone layer (AL) is the grain peripheral tissue; it is rich in micronutrients, vitamins, antioxidants, and essential amino acids. This highly nutritive part of the grain has been less studied partly because its isolation is so laborious. In the present study, the ALs of Triticum aestivum (variety Récital) were separated manually at 15 stages of grain development. A total of 327 proteins were identified using 2-DE LC-MS/MS. They were classified in six main groups and 26 sub-groups according to their biochemical function. Proteomic analysis revealed seven different profiles distributed among three main development stages: (i) early AL development, with proteins involved in intense metabolic activities in the growth and development of the cell wall compounds; (ii) the intermediate stage, characterized by oxidative stress and defense proteins (65%) linked with loss of water in peripheral layers during grain filling; and (iii) AL maturation, involving the production of amino acids and the control of reactive oxidative species to enable the accumulation and maturation of globulins within the AL. The present study provides the first insights into developing proteome in the AL. We describe the numerous AL enzymes involved in the accumulation of storage protein and in the protection of the endosperm over time.

The hand dissection of wheat aleurone layer (AL) was carried in this study for the first time on fifteen developmental stages from cell differentiation to grain maturity. Three major phases were revealed over AL development: cell division activities, globulins storage, and grain protection. Enzymes related to metabolites and vitamins were abundantly expressed during the two first phases. In parallel to the progressive globulins accumulation, the final phase was characterized by key enzyme synthesis involved in energy production, amino-acids and antioxidant synthesis plus others to face hypoxia and dehydration of grain tissues.