Water limitation and rootstock genotype interact to alter grape berry metabolism through transcriptome reprogramming

Grapevine is a perennial crop often cultivated by grafting a scion cultivar on a suitable rootstock.Rootstocks influence scions,particularly with regard to water uptake and vigor.Therefore,one of the possibilities to adapt viticulture to the extended drought stress periods is to select rootstocks conferring increased tolerance to drought.However,the molecular mechanisms associated with the ability of rootstock/scion combination to influence grape berry metabolism under drought stress are still poorly understood.The transcriptomic changes induced by drought stress in grape berries(cv.Pinot noir)from vines grafted on either 110R(drought-tolerant)or 125AA(drought-sensitive)rootstock were compared.The experiments were conducted in the vineyard for two years and two grape berry developmental stages(50%and 100%veraison).The genome-wide microarray approach showed that water stress strongly impacts gene expression in the berries,through ontology categories that cover cell wall metabolism,primary and secondary metabolism,signaling,stress,and hormones,and that some of these effects strongly depend on the rootstock genotype.Indeed,under drought stress,berries from vines grafted on 110R displayed a different transcriptional response compared to 125AA-concerning genes related to jasmonate(JA),phenylpropanoid metabolism,and pathogenesis-related proteins.The data also suggest a link between JA and secondary metabolism in water-stressed berries.Overall,genes related to secondary metabolism and JA are more induced and/or less repressed by drought stress in the berries grafted on the drought-sensitive rootstock 125AA.These rootstock-dependent gene expression changes are relevant for berry composition and sensory properties.

Behavioral syndrome in a native and an invasive hymenoptera species

Recent studies have focused on the role of behavior in biological invasions. Individuals may differ consistently in time for several behavioral traits （personality） which covary （behavioral syndrome） resulting in different behavioral types, some of them favoring invasion. Social hymenopterans have a strong potential to be invaders and their success depends primarily on the foundresses＇ ability to found viable colonies. They are expected to be active, explorative and bold for optimally establishing their nest. In Europe, 2 homet species coexist： the native Vespa crabro and the invasive Vespa velutina. These 2 species may compete for nesting sites and we suggest that the initial success of V. velutina has been favored by its behavior in outperforming V. crabro for the traits involved in nest initiation. Here, we （i） defined the personality of V. crabro and V：. velutina, （ii） tested for the existence of behavioral syndrome in these species, and （iii） compared their performances using an open-field test. Our results show that V. crabro foundresses behave consistently but not V. velutina; this lack of consistency being mainly due to reduced variance among individuals. This result questions the possibility of detecting consistent behavioral differences in species having recently undergone a strong bottleneck. Both species exhibit the same correlations between activity, boldness and exploration and V. velutina clearly outperforms 14. crabro for all traits. Our results suggest that activity, boldness, and exploration are implicated in both hornet nest initiation and invasion process which contributed to explain why social hymenopterans are so successful at colonization.

Spatial distribution of Vespa velutina individuals hunting at domestic honeybee hives： heterogeneity at a local scale

Since its recent introduction into Europe, the yellow-legged hornet, Vespa velutina, has become a major predator of the domestic honeybee, Apis mellifera, but little is known about its hunting behavior. We studied V. velutina hunting behavior by a capture- mark-recapture procedure in an experimental apiary. A total of 360 hornets were captured and tagged, and we determined： （i） the number of hornets visiting the apiary and the changes in time, （ii） the average number of individual visits per half-day and the time elapsed between consecutive recaptures, and （iii） the individual and global distribution of the hornets in the apiary. More than 50% of the marked hornets were recaptured at least once, this increased to 74% in considering the first marked individuals. We estimated 350 hornets visiting the patch daily with at least 1 visit per half-day. The number of marked hornets decreased over time while the number of unmarked ones increased, suggesting a turnover of individuals. The reduction of the delay between consecutive visits indicates that hornets became more efficient over time. Most of the hornets （88%） were recaptured in front of different hives but, overall, the global distribution was aggregative. Hornets were mainly recaptured in front of 1 hive which was neither the smallest nor the biggest colony, suggesting that the major cue used by hornets is not the amount of food. We hypothesize that the defensive behavior of the honeybee colony could explain our results which may be promising to further studies.