Role of ethylene on various ripening pathways and on the development of sensory quality of Charentais cantaloupe melons

Charentais melons (Cucumis melo L., var cantalupensis Naud.) in which ethylene biosynthesis has been suppressed by an antisense ACC oxidase gene have been used to better understand the role of ethylene in the regulation of the ripening process of climacteric fruit and on the development of sensory qualities. We have shown that a number of biochemical and molecular processes associated with the ripening of climacteric fruit are ethylene-independent. In some cases, such as softening of the flesh, the same pathway comprises both ethylene-dependent and -independent components. The various ethylene-dependent events exhibit differential sensitivity to ethylene. The threshold level for degreening of the rind is 1 ppm, while 2.5 ppm are required to trigger the ethylene-dependent component of the softening process. The saturating level of ethylene for all these events is less than 5 ppm, which is by far lower than the internal ethylene concentrations found in the fruit at the climacteric peak (around 100 ppm). Detachment of the fruit influences the development of respiratory climacteric. Fruit remaining attached to the vine, although producing higher levels of ethylene, exhibit a reduced climacteric rise in respiration as compared to detached fruit. The response of antisense ACO fruit to exogenous ethylene in terms of respiration is higher in detached than in attached fruit. Ethylene-suppressed melons show a severe reduction of aroma volatiles production, particularly in ester production. In the biosynthetic pathway of aliphatic esters, the dehydrogenation of fatty acids and aldehydes appears to be ethylene-dependent. In contrast, alcohol acetylation comprises ethylene-dependent and ethylene-independent components, probably corresponding to differentially regulated alcohol acetyl transferases. In terms of sensory quality, these data show that the extension of shelf-life through the inhibition of ethylene production has some beneficial effects on texture and sugar accumulation but is detrimental for the generation of aroma

Two highly divergent alcohol dehydrogenases of melon exhibit fruit ripening-specific expression and distinct biochemical characteristics

Alcohol dehydrogenases (ADH) participate in the biosynthetic pathway of aroma volatiles in fruit by interconverting aldehydes to alcohols and providing substrates for the formation of esters. Two highly divergent ADH genes (15% identity at the amino acid level) of Cantaloupe Charentais melon (Cucumis melo var. Cantalupensis) have been isolated. Cm-ADH1 belongs to the medium-chain zinc-binding type of ADHs and is highly similar to all ADH genes expressed in fruit isolated so far. Cm-ADH2 belongs to the short-chain type of ADHs. The two encoded proteins are enzymatically active upon expression in yeast. Cm-ADH1 has strong preference for NAPDH as a co-factor, whereas Cm-ADH2 preferentially uses NADH. Both Cm-ADH proteins are much more active as reductases with Kms 10–20 times lower for the conversion of aldehydes to alcohols than for the dehydrogenation of alcohols to aldehydes. They both show strong preference for aliphatic aldehydes but Cm-ADH1 is capable of reducing branched aldehydes such as 3-methylbutyraldehyde, whereas Cm-ADH2 cannot. Both Cm-ADH genes are expressed specifically in fruit and up-regulated during ripening. Gene expression as well as total ADH activity are strongly inhibited in antisense ACC oxidase melons and in melon fruit treated with the ethylene antagonist 1-methylcyclopropene (1-MCP), indicating a positive regulation by ethylene. These data suggest that each of the Cm-ADH protein plays a specific role in the regulation of aroma biosynthesis in melon fruit

Deep Brain Stimulation in Moroccan Patients With Parkinson's Disease: The Experience of Neurology Department of Rabat

Introduction: Deep brain stimulation (DBS) of the subthalamic nucleus (STN) is known as a therapy of choice of advanced Parkinson's disease. The present study aimed to assess the beneficial and side effects of STN DBS in Moroccan Parkinsonian patients.Material and Methods: Thirty five patients underwent bilateral STN DBS from 2008 to 2016 in the Rabat University Hospital. Patients were assessed preoperatively and followed up for 6 to 12 months using the Unified Parkinson's Disease Rating Scale in four conditions (stimulation OFF and ON and medication OFF and ON), the levodopa-equivalent daily dose (LEDD), dyskinesia and fluctuation scores and PDQ39 scale for quality of life (QOL). Postoperative side effects were also recorded.Results: The mean age at disease onset was 42.31 ± 7.29 years [28–58] and the mean age at surgery was 54.66 ± 8.51 years [34–70]. The median disease duration was 11.95 ± 4.28 years [5–22]. Sixty-three percentage of patients were male. 11.4% of patients were tremor dominant while 45.71 showed akinetic-rigid form and 42.90 were classified as mixed phenotype. The LEDD before surgery was 1200 mg/day [800-1500]. All patients had motor fluctuations whereas non-motor fluctuations were present in 61.80% of cases. STN DBS decreased the LEDD by 51.72%, as the mean LEDD post-surgery was 450 [188-800]. The UPDRS-III was improved by 52.27%, dyskinesia score by 66.70% and motor fluctuations by 50%, whereas QOL improved by 27.12%. Post-operative side effects were hypophonia (2 cases), infection (3 cases), and pneumocephalus (2 cases).Conclusion: Our results showed that STN DBS is an effective treatment in Moroccan Parkinsonian patients leading to a major improvement of the most disabling symptoms (dyskinesia, motor fluctuation) and a better QOL

The MtMMPL1 Early Nodulin Is a Novel Member of the Matrix Metalloendoproteinase Family with a Role in Medicago truncatula Infection by Sinorhizobium meliloti1[W][OA]

We show here that MtMMPL1, a Medicago truncatula nodulin gene previously identified by transcriptomics, represents a novel and specific marker for root and nodule infection by Sinorhizobium meliloti. This was established by determining the spatial pattern of MtMMPL1 expression and evaluating gene activation in the context of various plant and bacterial symbiotic mutant interactions. The MtMMPL1 protein is the first nodulin shown to belong to the large matrix metalloendoproteinase (MMP) family. While plant MMPs are poorly documented, they are well characterized in animals as playing a key role in a number of normal and pathological processes involving the remodeling of the extracellular matrix. MtMMPL1 represents a novel MMP variant, with a substitution of a key amino acid residue within the predicted active site, found exclusively in expressed sequence tags corresponding to legume MMP homologs. An RNA interference approach revealed that decreasing MtMMPL1 expression leads to an accumulation of rhizobia within infection threads, whose diameter is often significantly enlarged. Conversely, MtMMPL1 ectopic overexpression under the control of a constitutive (35S) promoter led to numerous abortive infections and an overall decrease in the number of nodules. We discuss possible roles of MtMMPL1 during Rhizobium infection

Role of ethylene in the biosynthetic pathway of aliphatic ester aroma volatiles in Charentais Cantaloupe melons

Compared to other melon types, Cantaloupe Charentais melons are highly aromatic with a major contribution to the aroma being made by aliphatic and branched esters. Using a transgenic line in which the synthesis of the plant hormone ethylene has been considerably lowered by antisense ACC oxidase mRNA (AS), the aliphatic ester pathway steps at which ethylene exerts its regulatory role were found. The data show that the production of aliphatic esters such as hexyl and butyl acetate was blocked in AS fruit and could be reversed by ethylene. Using fruit discs incubated in the presence of various precursors, the steps at which ester formation was inhibited in AS fruit was shown to be the reduction of fatty acids and aldehydes, the last step of acetyl transfer to alcohols being unaffected. However, treating AS fruit with the ethylene antagonist 1-methylcyclopropene resulted in about 50% inhibition of acetyl transfer activity, indicating that this portion of activity was ethylene-dependent and this was supported by the low residual ethylene concentration of AS fruit discs (around 2 µl l-1). In conclusion, the reduction of fatty acids and aldehydes appears essentially to be ethylene-dependent, whilst the last step of alcohol acetylation has ethylene-dependent and ethylene-independent components, probably corresponding to differentially regulated alcohol acetyltransferases

Expression Profiling in Medicago truncatula Identifies More Than 750 Genes Differentially Expressed during Nodulation, Including Many Potential Regulators of the Symbiotic Program

In this study, we describe a large-scale expression-profiling approach to identify genes differentially regulated during the symbiotic interaction between the model legume Medicago truncatula and the nitrogen-fixing bacterium Sinorhizobium meliloti. Macro- and microarrays containing about 6,000 probes were generated on the basis of three cDNA libraries dedicated to the study of root symbiotic interactions. The experiments performed on wild-type and symbiotic mutant material led us to identify a set of 756 genes either up- or down-regulated at different stages of the nodulation process. Among these, 41 known nodulation marker genes were up-regulated as expected, suggesting that we have identified hundreds of new nodulation marker genes. We discuss the possible involvement of this wide range of genes in various aspects of the symbiotic interaction, such as bacterial infection, nodule formation and functioning, and defense responses. Importantly, we found at least 13 genes that are good candidates to play a role in the regulation of the symbiotic program. This represents substantial progress toward a better understanding of this complex developmental program