The Plant Short-Chain Dehydrogenase (SDR) superfamily:genome-wide inventory and diversification patterns

Background Short-chain dehydrogenases/reductases (SDRs) form one of the largest and oldest NAD(P)(H) dependent oxidoreductase families. Despite a conserved 'Rossmann-fold' structure, members of the SDR superfamily exhibit low sequence similarities, which constituted a bottleneck in terms of identification. Recent classification methods, relying on hidden-Markov models (HMMs), improved identification and enabled the construction of a nomenclature. However, functional annotations of plant SDRs remain scarce. Results Wide-scale analyses were performed on ten plant genomes. The combination of hidden Markov model (HMM) based analyses and similarity searches led to the construction of an exhaustive inventory of plant SDR. With 68 to 315 members found in each analysed genome, the inventory confirmed the over-representation of SDRs in plants compared to animals, fungi and prokaryotes. The plant SDRs were first classified into three major types --- 'classical', 'extended' and 'divergent' --- but a minority (10 % of the predicted SDRs) could not be classified into these general types ('unknown' or 'atypical' types). In a second step, we could categorize the vast majority of land plant SDRs into a set of 49 families. Out of these 49 families, 35 appeared early during evolution since they are commonly found through all the Green Lineage. Yet, some SDR families --- tropinone reductase-like proteins (SDR65C), 'ABA2-like'-NAD dehydrogenase (SDR110C), 'salutaridine/menthone-reductase-like' proteins (SDR114C), 'dihydroflavonol 4-reductase'-like proteins (SDR108E) and 'isoflavone-reductase-like' (SDR460A) proteins --- have undergone significant functional diversification within vascular plants since they diverged from Bryophytes. Interestingly, these diversified families are either involved in the secondary metabolism routes (terpenoids, alkaloids, phenolics) or participate in developmental processes (hormone biosynthesis or catabolism, flower development), in opposition to SDR families involved in primary metabolism which are poorly diversified. Conclusion The application of HMMs to plant genomes enabled us to identify 49 families that encompass all Angiosperms ('higher plants') SDRs, each family being sufficiently conserved to enable simpler analyses based only on overall sequence similarity. The multiplicity of SDRs in plant kingdom is mainly explained by the diversification of large families involved in different secondary metabolism pathways, suggesting that the chemical diversification that accompanied the emergence of vascular plants acted as a driving force for SDR evolution

Impact of organic and inorganic fertilizers on tomato vigor, yield and fruit composition under tropical andosol soil conditions

Introduction. Little is known about the impact of organic manure on andosol. Materials and methods. Two varieties of Solanum lycopersicum L. (cvs. ‘Rio grande’ and ‘Rossol VFN’) were grown under tropical andosol. The soil was silty, acidic and very poor in Bray P (3 mg·kg–1) with a strong imbalance in the (Ca:Mg:K) ratio of (74.0:25.0:0.7). Five fertilization treatments were used: (i) control with no fertilizer, (ii) minerals, with a (Ca:Mg:K) ratio of (76:18:6) and 75 mg P·kg–1 of soil; (iii) poultry manure with a (Ca:Mg:K) ratio of (68:24:7) and 450 mg P·kg–1 of soil; (iv) a combination of (ii) and (iii), and (v) mineral fertilization as applied by local farmers, with a (Ca:Mg:K) ratio of (73:25:1) and 54 mg P·kg–1 of soil. Results. All cation-balanced treatments (organic, mineral or a combination of both) significantly improved plant growth, the number of trusses and fruits per plant, the marketable fruit yield and fruit P, K, Ca and Na contents of both tomato varieties considered. The ‘Rio grande’ variety was the most productive (32–44 t·ha–1) compared with the ‘Rossol’ variety (20–22 t·ha–1). There was no major difference between the organic fertilizer and the cation-balanced mineral fertilizer. There was no effect of mineral fertilizer with an unbalanced cation composition on tomato plant growth and production as compared with unfertilized control. Conclusion. In tropical andosol poor in potassium and phosphorous and with excess of Mg, application of poultry manure in adequate dosage and at the right time is capable of sustaining tomato fruit production, as well as the application of calculated inorganic fertilizer

Field management of Taro (Colocasia esculenta (L.) Schott) leaf blight via fungicidal spray of foliage

Taro leaf blight (TLB) epidemic hit Cameroon for the first time in 2009. Since then, the disease is persistent and its typical devastating legacy is threatening Taro (Colocasia esculenta) in the North and South West Regions of Cameroon. This study was initiated with the objective to determine the potentials of some fungicides to control TLB. The experimental design was completely randomized with a 3x15x2 factorial, including 3 treatments: T1 (Callomil plus72WP), T2 (Mancoxyl plus 720WP) and T3, 1:1 ratio T1 + T2 all applied at concentrations of 4g/L; 15 repetitions and 2 planting seasons (dry season i.e. October 2014 – March 2015 and rainy season i.e. April-October 2015). Disease incidence and disease severity were used to evaluate the disease progression while corm yield was used to appraise the economic injury. The results revealed disease incidence of 0% during the dry season and 18.2%, 27.3% and 100%, for T1, T2 and T3 and control during rainy season respectively. Disease severity was 75% in control and only 1% for the different treatments. Corm yield in the rainy season was 17.4kg, 15.08kg, 14.27kg and 5.89kg for T1, T2, T3 and control respectively. This study suggests that TLB epidemic can effectively be managed by foliage spray with Metalaxyl containing fungicides at a weekly dosage of 4g/L. Key words: Chemical control, Colocasia esculenta, Epidemic, Phytopathology, Phytophthora colocasia

Phytiatrie et fonction du phytiatre en phytoprotection

La phytiatrie est une branche de la phytoprotection dont la définition est peu claire, variable et très confuse dans la littérature. Dans cet article dont les données sont issues de sources secondaires, nous essayons de : (1) clarifier la définition des mots phytiatrie et phytiatre ; (2) préciser le contenu d’une formation de base en phytiatrie ; (3) proposer une organisation de la fonction de phytiatre. Le phytiatre (médecin de la plante), s’occupe de la gestion des maladies, des agresseurs et des traumatismes des plantes. La phytiatrie se distingue clairement de la phytopathologie, science qui étudie les maladies des plantes causées par les microorganismes et les facteurs environnementaux. Le phytiatre a des connaissances en phytopharmacie, mais n’est pas un phytopharmacien. Le diplômé en phytiatrie doit être capable d’analyser et de comprendre les exigences de la phytoprotection afin de développer et de proposer des solutions adéquates, dans un contexte de protection de l’environnement. Le grade de phytiatre devrait être réservé aux ingénieurs en phytiatrie, aux titulaires d’un Master ou d'un Doctorat / Ph.D en phytiatrie. Une meilleure structuration des formations en phytiatrie et de la fonction de phytiatre, peut contribuer à une meilleure prise en charge des affections des plantes dans les systèmes de production en Afrique. English title: Phytiatrics and function of the phytiatrist in plant protection Abstract Phytiatrics is a branch of Phytoprotection whose definition is unclear, variable and very confused in the literature. In this article, whose data come from secondary sources, we try to: (1) clarify the definition of phytiatrics and phytiatrist; (2) specify the content of basic training in phytiatrics; (3) propose an organization of the function of phytiatrist. The phytiatrist (plant medical doctor) deals with the management of plant diseases, pests and trauma. Phytiatrics is clearly distinguished from phytopathology which is the science that studies plant diseases caused by microorganisms and environmental factors. The phytiatrist has knowledge in phytopharmacy, but is not a phytopharmacist. The graduate in phytiatrics must be able to analyze and understand the requirements of phytoprotection in order to develop and propose adequate solutions, in a context of environmental protection. The rank of phytiatrist should be reserved for engineers in phytiatrics, holders of a Master’s degree or a doctorate in phytiatrics. A better structuring of training in phytiatrics and the function of phytiatrist can contribute to better management of plant ailments in plant production systems in Africa. Keywords: plant, disease, aggressors, training, phytiatrist

Functional characterization of SlscADH1, a fruit-ripening associated short-chain alcohol dehydrogenase of tomato

A tomato short-chain dehydrogenase-reductase (SlscADH1) is preferentially expressed in fruit with a maximum expression at the breaker stage while expression in roots, stems, leaves and flowers is very weak. It represents a potential candidate for the formation of aroma volatiles by interconverting alcohols and aldehydes. The SlscADH1 recombinant protein produced in Escherichia coli exhibited dehydrogenase-reductase activity towards several volatile compounds present in tomato flavour with a strong preference for the NAD/NADH co-factors. The strongest activity was observed for the reduction of hexanal (Km = 0.175 mM) and phenylacetaldehyde (Km = 0.375 mM) in the presence of NADH. The oxidation process of hexanol and 1-phenylethanol was much less efficient (Kms of 2.9 and 23.0 mM, respectively), indicating that the enzyme preferentially acts as a reductase. However activity was observed only for hexanal, phenylacetaldehyde, (E)-2-hexenal and acetaldehyde and the corresponding alcohols. No activity could be detected for other aroma volatiles important for tomato flavour, such as methyl-butanol/methyl-butanal, 5-methyl-6-hepten-2-one/5-methyl-6-hepten-2-ol, citronellal/citronellol, neral/nerol, geraniol. In order to assess the function of the SlscADH1 gene, transgenic plants have been generated using the technique of RNA interference (RNAi). Constitutive down-regulation using the 35S promoter resulted in the generation of dwarf plants, indicating that the SlscADH1 gene, although weakly expressed in vegetative tissues, had a function in regulating plant development. Fruitspecific down-regulation using the 2A11 promoter had no morphogenetic effect and did not alter the aldehyde/alcohol balance of the volatiles compounds produced by the fruit. Nevertheless, SlscADH1-inhibited fruit unexpectedly accumulated higher concentrations of C5 and C6 volatile compounds of the lipoxygenase pathway, possibly as an indirect effect of the suppression of SlscADH1 on the catabolism of phospholipids and/or integrity of membranes

Phenolic content and antioxidant activity of young and mature mango (Mangifera indica) and avocado (Persea americana) leave extracts

Polyphenols are groups of secondary metabolites in plants, known with their various biological activities, including their ability to act as antioxidants. Due to the side effects of the use of synthetic antioxidants on human’s health, the search for natural less toxic compounds has significantly increased. This study was carried out to evaluate the phenolic content and antioxidant activity of young and mature avocado (Persea americana) and mango leaves (Mangifera indica). Different extracts were prepared by maceration in methanol, ethanol, cold and hot water. The phenolic content of the extracts was determined using the Folic-Ciocalteu Method. A total of three antioxidant tests were done on the extracts: the 2, 2-diphenyl-1-picrylhydrazyl test (DPPH test), the Ferric reducing antioxidant power and the Hydroxyl radical scavenging activity. Results of these investigations generally showed that the mature leaves of mango and young leaves of avocado exhibited the highest phenolic and flavonoid contents, as well as the antioxidant activity. They can be recommended as good sources of antioxidants to reduce the damages caused by free radicals and reactive oxygenated species in the body. They can also be recommended as a source of antioxidants for the preservation of oils, food containing lipids and pharmaceutical products

Nutrient Accumulation in Leaves and Soft Twigs of \u3ci\u3eMoringa oleifera\u3c/i\u3e Lam. at Different Growth Stages in Western Highland of Cameroon

Moringa oleifera belongs to the Moringaceae family and is considered to have its origin in the south of the Himalayan mountains. The species is being introduced into the highland zone of Cameroon. It is a tree which has many valuable properties and it is of great nutritional and scientific interest. The objective of this experiment was to evaluate nutrient composition in leaves and soft twigs of M. oleifera at different growth heights when grown in the Western Highland of Cameroon

Effects of Salt Stress on Plant Growth, Nutrient Partitioning, Chlorophyll Content, Leaf Relative Water Content, Accumulation of Osmolytes and Antioxidant Compounds in Pepper (Capsicum annuum L.) Cultivars

The salinity of soil is among the most important abiotic stresses which limit agricultural productivity worldwide. The effects of salinity on growth, nutrient partitioning, chlorophyll, leaf relative water content, osmolytes accumulation and antioxidant compounds of pepper (Capsicum annuum L.) cultivars (‘Granada’, ‘Goliath’ and ‘Nobili’), widely used in Cameroon, were investigated. Plants were subjected to four levels of NaCl (0, 50, 100 and 200 mM) at early seedling growth stage of plant development. Application of NaCl treatment led to a significant increase in total  soluble  sugars,  proline; soluble proteins; total free amino acids content, peroxydase and superoxide dismutase activity and total phenolic content in salt-tolerant ‘Granada’ and ‘Nobili’ compared to salt-sensitive ‘Goliath’ and untreated plants, on the contrary, decreased in root dry weight, shoot dry weight, number of leaves, shoot length, stem diameter, total leaf area, chlorophyll and leaf relative water content in ‘Goliath’ at low salinity level. Flavonoid content, K, Ca and Mg concentrations were significantly reduced with increasing salinity in all cultivars. The highest Na concentrations were detected in the leaves while the lowest were recorded in the roots of ‘Goliath’ at high salinity level. The salt sensitivity of ‘Goliath’ seems to be increased osmotic adjustment through the strongly accumulation of Na in leaves while the salt tolerance of ‘Granada’ was related to its induce of antioxidative enzyme system more efficiently, resulting in higher osmolytes accumulation under salinity. ‘Granada’ was more tolerant and stable in physiological and biochemical traits suggesting that it could be grown in salt-affected soils