Cloning, characterization and differential expression of a Bowman–Birk inhibitor during progressive water deficit and subsequent recovery in peanut (Arachis hypogaea) leaves

Bowman–Birk inhibitor (BBI) genes encode serine protease inhibitors well known for their anticarcinogenic properties and roles in plant defense against insects and pathogens. Here we investigated the expression of a BBI gene in response to water deficit, recovery and phytohormones. A full length cDNA encoding a novel BBI (AhBBI) was isolated from peanut (Arachis hypogaea L.) leaves. The deduced protein is a polypeptide of 11.5 kDa containing a signal peptide of 20 amino acids which is missing from peanut seed full-length BBI. Sequence analysis showed that AhBBI presents the characteristic features of BBIs but its first inhibitory loop is unique among the Fabaceae species. Real-time PCR analyses indicated that in peanut leaves, AhBBI is upregulated by water deficit and exogenous jasmonic acid (JA) but repressed by abscissic acid (ABA) after 24 h of treatment. The transcripts accumulation patterns during water deficit differed between two cultivars studied in relation to their tolerance levels to drought. AhBBI transcripts accumulated earlier and stronger in the tolerant cultivar (cv. Fleur11) compared to the susceptible one (cv. 73–30) suggesting that BBI genes are involved in drought stress tolerance. Subsequent rehydration reversed the accumulation of AhBBI transcripts in both cultivars but at different levels. The overall role of BBI in abiotic stress tolerance and the possible mechanisms of action are discussed

Adaptation à la sécheresse et création variétale : le cas de l’arachide en zone sahélienne

Drought is a multiform constraint expressing at different plant organisation levels. It is recognised as the first factor limiting the agriculture production in the world. The Sahel subtropical regions were the most exposed to the devasting effects of the recent climate change. A state of knowledge referring to the plant responses to drought is a fundamental initial step to any program of selection. This review concerns more particularly groundnut (Arachis hypogaea L.), which is a very common legume in the Sahel areas. Critical evaluations of traits as relevant selection criteria for a breeding program aiming at improving yield and yield stability under drought constraint were made. The genetic specificities of the species are exposed in the first part. Then a detailed description of the grain-legume traits related to drought adaptation is presented. The review was widened to other plants for the molecular responses to water deficit, supposed to be more general. Finally, the last part supplied an updated synthesis of the recent advances in biotechnology on groundnut with special focus on drought tolerance

Adaptation à la sécheresse et création variétale : le cas de l’arachide en zone sahélienne

Drought is a multiform constraint whose impact on the vegetal metabolism is very variable according to its duration, intensity and phenological stage of the vegetal development where it occurs. Thus, the plant resistance is expressed at different plant organisation levels. The present study was aimed at integrating knowledge generated by experiments carried out in Senegal on groundnut within the framework of a breeding programme geared towards improving groundnut yield under drought conditions. Three studies involved in the breeding work, are presented. The first chapter analyses an incomplete half-diallel cross performed on an original population under recurrent selection for drought adaptation. The study confirmed the weak heritability of yields but concludes that the best predictor of pod-yield was the pod-yield itself. By contrast, the study of the genetic correlations showed that a selection for high haulm-yield could lead to poor pod-maturity under drought constraint. The selection indices were performed and used to estimate genetic gains relative to the main agronomic characters according to selection pressure. The second chapter covers the genetic variability of phenological, agronomic and physiological characters studied in two series of quasi-isogenic early lines. It has indicated that genetic variability was expressed in these lines despite its closeness. Some correlations between yield and physiological parameters, i.e. mainly fluorescence parameters, were significant but not stable across lines and environments showing that groundnut have different drought adaptation strategies according to genetic background and drought pattern. This work was pursued at the molecular level with three reference cvs involving the both recurrent parents of the precedent study. The gene transcript kinetics under drought, obtained using RT-PCR, showed that Phospolipase D and Cysteine protease gene expressions were stimulated by stress in the most susceptible cultivars, whereas their was higher LEA gene expression in the resistant one. These interconnected experiments conducted at different plant organisation levels led to the development of a general methodological model and of new improved genotypes to meet the social demand