• water stress
• Vigna unguiculata
• stress proteins
• semi-quantitative RT-PCR
• molecular marker
• gene variability
• gene expression
• drought stress tolerance
• drought
• dehydrins
• Cowpea
• chilling tolerance
• Western blot

Abstract
Cowpea (Vigna unguiculata (L.) Walp) is a tropical grain legume, which plays an important nutritional role in developing countries of the tropics and subtropics, especially in sub-Saharian Africa, Asia, Central and South America. Its production is limited by a lot of environmental stresses and drought seems to be one of the most important. It has been reported that cowpea has in its genome genes encoding proteins associated with environmental stresses. Among the stress induced proteins there is a group called dehydrins. They are produced on the last stages of embryogenesis or in response to drought, salinity, low temperature or to ABA application. It has been hypothesized that dehydrins function by stabilizing large-scale hydrophobic interactions, such as membrane structures or hydrophobic patches of proteins. We hypothesized that, as dehydrins have been proposed to protect cellular macromolecules and their expression increase in response to dehydration, it should be used as molecular marker for drought stress tolerance. To test this hypothesis, a fragment of dehydrin was amplified and used for analysis of variability dehydrin gene and cowpea. We used also semi-quantitative RT-PCR (Reverse transcription PCR) to evaluate dehydrin gene expression in plants subjected to water stress. An anti-dehydrin antibody was used to study dehydrin protein accumulation under water stress. Analysis of the dehydrin gene variability revealed a high diversity of this protein family and a high identity to Vigna unguiculata dehydrin database associated to chilling tolerance. Expression of dehydrins was high on the wild ecotypes evidencing more adaptability of this group to water deficit. Western blot analysis revealed an apparent absence of dehydrins in leaves and a presence of a constitutive dehydrin in seeds of unstressed plants.