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Orange fruit abscission usually occurs at the final stage of fruit maturation but in some areas of citrus production, in advance of the usual harvest period, and sometimes suddenly and intensely. The reasons for this precocious citrus fruit abscission remains unclear. Therefore, the aim of this study was to try to clarify what the determinants of this phenomenon are. A multi-site experimentation was carried out on six orange cultivars, in Corsica, Spain and Tunisia where the phenomenon of early massive fruit drop varies. Climatic parameters, fruit maturity parameters and fruit detachment force (FDF) were recorded along the fruit maturation period. Respectively to the fruit drop, the FDF decreased in Tunisia and in Spain until the fruit falls, whereas in Corsica, it remained relatively constant throughout fruit maturation. Although data on fruit maturity parameters (rind color, acidity and total soluble solids) differed at the three sites, their evolution was similar during the period of maturation. FDF was not related to changes in any fruit maturity parameters, and more likely depended on changes in temperatures on days when the mean temperature was above 13 &deg, C. Massive fruit abscission could be linked to the earlier more rapid restart of vegetative growth in Tunisia and Spain than in Corsica.

International audience; Genome editing, which is an unprecedented technological breakthrough, has provided a valuable means of creating targeted mutations in plant genomes. In this study, we developed a genomic web tool to identify all gRNA target sequences in the coffee genome, along with potential off-targets. In all, 8,145,748 CRISPR guides were identified in the draft genome of Coffea canephora corresponding to 5,338,568 different sequences and, of these, 4,655,458 were single, and 514,591 were covering exons. The proof of concept was established by targeting the phytoene desaturase gene (CcPDS) using the Agrobacterium tumefaciens transformation technique and somatic embryogenesis as the plant regeneration method. An analysis of the RNA-guided genome-editing events showed that 22.8% of the regenerated plants were heterozygous mutants and 7.6% were homozygous mutants. Mutation efficiency at the target site was estimated to be 30.4%. We demonstrated that genome editing by the CRISPR/Cas9 method is an efficient and reliable way of knocking out genes of agronomic interest in the coffee tree, opening up the way for coffee molecular breeding. Our results also showed that the use of somatic embryogenesis, as the method for regenerating genome-edited plants, could restrict the choice of targeted genes to those that are not essential to the embryo development and germination steps

International audience

The taxonomic position of the family Castniidae within the order Lepidoptera has changed over time. Initially, it was classified in the superfamily Sesioidea, and then it was grouped in a large assemblage including the Cossoidea, Sesioidea, and Zygaenoidea. Recent studies have included it in the superfamily Cossoidea. In Europe, the palm borer moth (PBM) Paysandisia archon is the only species of the Castniidae. This moth, native to South America (Argentina and Uruguay), was first reported in Europe (France and Spain) in 2001, but it is believed to have been introduced before 1995 on palm trees imported from Argentina. Since then, the moth has been reported in Belgium, Bulgaria, Cyprus Island, Croatia, the Czech Republic, Denmark, France, Greece, Italy, Slovenia, Spain, Switzerland, and the United Kingdom. All known hosts are palms (family Arecaceae). The moth appears to have a wide host range, including the native Mediterranean palms but also exotic species, threatening ornamental and patrimonial palms, as well as date palms in North Africa. In Europe, the adult moths are active during the hottest part of sunny days, from mid-May to September–October, with a peak during June and July. PBM overwinter as larvae. Cocoons can be found from mid-March to mid-September. During the summer, all of the developmental stages of the moth (egg, larva, pupa, and adult) can be observed. Recent research has aimed to provide a more comprehensive understanding of the PBM's biology and host palm tree range under European Mediterranean conditions, to fill the knowledge gaps, support decisions for risk assessment, and improve monitoring, management, and regulation. (Resume d'auteur)

There are well-recognized sex differences in many pituitary endocrine axes, usually thought to be generated by gonadal steroid imprinting of the neuroendocrine hypothalamus. However, the recognition that growth hormone (GH) cells are arranged in functionally organized networks raises the possibility that the responses of the network are different in males and females. We studied this by directly monitoring the calcium responses to an identical GH-releasing hormone (GHRH) stimulus in populations of individual GH cells in slices taken from male and female murine GH-eGFP pituitary glands. We found that the GH cell network responses are sexually dimorphic, with a higher proportion of responding cells in males than in females, correlated with greater GH release from male slices. Repetitive waves of calcium spiking activity were triggered by GHRH in some males, but were never observed in females. This was not due to a permanent difference in the network architecture between male and female mice; rather, the sex difference in the proportions of GH cells responding to GHRH were switched by postpubertal gonadectomy and reversed with hormone replacements, suggesting that the network responses are dynamically regulated in adulthood by gonadal steroids. Thus, the pituitary gland contributes to the sexually dimorphic patterns of GH secretion that play an important role in differences in growth and metabolism between the sexes.

In plants, polyglutamylated folate forms account for a significant proportion of the total folate pool. Polyglutamylated folate forms are produced by the enzyme folylpolyglutamate synthetase (FPGS). The FPGS enzyme is encoded by two genes in rice, Os03g02030 and Os10g35940. Os03g02030 represents the major expressed form in developing seed. To determine the function of this FPGS gene in rice, a T-DNA knockout line was characterised. Disrupting Os03g02030 gene expression resulted in delayed seed filling. LC-MS/MS-based metabolite profiling revealed that the abundance of mono- and polyglutamylated folate forms was significantly decreased in seeds of the knockout line. RT-qPCR detected an increase in the transcript abundance of folate biosynthesis genes in seed of the knockout plant, whereas the folate deglutamating enzyme γ-glutamyl hydrolase mRNA level was reduced. Our study has uncovered a novel role for folate polyglutamylation during rice seed development and a potential feedback mechanism to maintain folate abundance.

International audience

Haploïdy

Haploïdy

Le tissu osseux est un tissu conjonctif qui a la particularité de se minéraliser. Ceci confère à l’os ses propriétés de banque minérale et de soutien mécanique de l’organisme. De son bon développement dépend celui de tous les autres tissus. Il est ainsi mis en place très tôt au cours de la période foetale et reste sous étroit contrôle, notamment endocrinien (GH et IGF-1), pendant toute la croissance mais aussi chez l’adulte dont le tissu osseux est le siège d’un remodelage permanent. La physiologie du développement du tissu osseux est bien connue, en particulier lorsqu’elle concerne l’ostéogenèse et la croissance des os longs. Le cartilage de conjugaison est le principal responsable de la croissance en longueur d’un os long, puisqu’il est le siège de la prolifération des chondrocytes ainsi que de l’ossification endochondrale, mécanisme par lequel le cartilage est transformé en os. La minéralisation de cet os néoformé constitue alors le stade ultime du développement du tissu osseux : elle se caractérise par la précipitation de cristaux d’hydroxyapatite au sein d’une matrice organique riche en collagène de type I. Des méthodes d’évaluation de plus en plus spécifiques (histomorphométrie et dosage sérique de l’ostéocalcine) peuvent être utilisées pour apprécier l’effet des principaux facteurs de variation de la croissance osseuse ; une meilleure connaissance de ces derniers permet d’envisager la possibilité de pouvoir agir directement sur l’os., As a mineralized connective tissue, bone is both the mineral bank and the mechanical support of the body. Its development influences the development of all the other tissues. Its differentiation takes place early in the fetus and its development continues during the growth period under strict regulation (GH and IGF-1). In adults, bone undergoes a permanent remodelling. The developmental physiology of bone is well known, particularly osteogenesis and long bone growth. The growth-plate, in which chondrocytes proliferate, plays a major role in the growth in length of the bone. It induces the endochondral ossification (transformation of cartilage into bone). The mineralization of the newly synthesized bone matrix constitutes the last stage of bone development : it is characterized by the precipitation of hydroxyapatite crystals inside the organic matrix enriched in type I collagen. Specific methods have been developed (bone histomorphometry, radioimmunoassay of osteocalcin) to study the effects of regulating factors on bone growth, in order to consider the use of these factors in the future as a possible way of directly modulating bone growth.