RESUMO
Tocopherols are non-polar compounds synthesized in the plastids, which function as major antioxidants of the plant cells and are essential in the human diet. Both the intermediates and final products of the tocopherol biosynthetic pathway must cross plastid membranes to reach their sites of action. So far, no protein with tocopherol binding activity has been reported in plants. Here, we demonstrated that the tomato SlTBP protein is targeted to chloroplasts and able to bind α-tocopherol. SlTBP-knockdown tomato plants exhibited reduced levels of tocopherol in both leaves and fruits. Several tocopherol deficiency phenotypes were apparent in the transgenic lines, such as alterations in photosynthetic parameters, dramatic distortion of thylakoid membranes and significant variations in the lipid profile. These results, along with the altered expression of genes related to photosynthesis, and tetrapyrrole, lipid, isoprenoid, inositol/phosphoinositide and redox metabolism, suggest that SlTBP may act in conducting tocopherol (or its biosynthetic intermediates) between the plastid compartments and/or at the interface between chloroplast and endoplasmic reticulum membranes, affecting interorganellar lipid metabolism.
Assuntos
Proteínas de Transporte/metabolismo , Proteínas de Plantas/metabolismo , Solanum lycopersicum/metabolismo , alfa-Tocoferol/metabolismo , Cloroplastos/metabolismo , Retículo Endoplasmático/metabolismo , Técnicas de Silenciamento de Genes , Metabolismo dos Lipídeos , Solanum lycopersicum/genética , Filogenia , Proteínas de Plantas/genética , Plastídeos/metabolismoRESUMO
KEY MESSAGE: Cowpea reproductive tools. Vigna unguiculata L. Walp. (cowpea) is recognized as a major legume food crop in Africa, but seed yields remain low in most varieties adapted to local conditions. The development of hybrid cowpea seed that could be saved after each generation, enabling significant yield increases, will require manipulation of reproductive development from a sexual to an asexual mode. To develop new technologies that could support the biotechnological manipulation of reproductive development in cowpea, we examined gametogenesis and seed formation in two transformable, African-adapted, day-length-insensitive varieties. Here, we show that these two varieties exhibit distinct morphological and phenological traits but share a common developmental sequence in terms of ovule formation and gametogenesis. We present a reproductive calendar that allows prediction of male and female gametogenesis on the basis of sporophytic parameters related to floral bud size and reproductive organ development, determining that gametogenesis occurs more rapidly in the anther than in the ovule. We also show that the mode of megagametogenesis is of the Polygonum-type and not Oenothera-type, as previously reported. Finally, we developed a whole-mount immunolocalization protocol and applied it to detect meiotic proteins in the cowpea megaspore mother cell, opening opportunities for comparing the dynamics of protein localization during male and female meiosis, as well as other reproductive events in this emerging legume model system.