Ripening and rot:How ripening processes influence disease susceptibility in fleshy fruits

Fleshy fruits become more susceptible to pathogen infection when they ripen;for example,changes in cell wall properties related to softening make it easier for pathogens to infect fruits.The need for high-quality fruit has driven extensive research on improving pathogen resistance in important fruit crops such as tomato(Solanum lycopersicum).In this review,we summarize current progress in understanding how changes in fruit properties during ripening affect infection by pathogens.These changes affect physical barriers that limit pathogen entry,such as the fruit epidermis and its cuticle,along with other defenses that limit pathogen growth,such as preformed and induced defense compounds.The plant immune system also protects ripening fruit by recognizing pathogens and initiating defense responses involving reactive oxygen species production,mitogen-activated protein kinase signaling cascades,and jasmonic acid,salicylic acid,ethylene,and abscisic acid signaling.These phytohormones regulate an intricate web of transcription factors(TFs)that activate resistance mechanisms,including the expression of pathogenesis-related genes.In tomato,ripening regulators,such as RIPENING INHIBITOR and NON_RIPENING,not only regulate ripening but also influence fruit defenses against pathogens.Moreover,members of the ETHYLENE RESPONSE FACTOR(ERF)family play pivotal and distinct roles in ripening and defense,with different members being regulated by different phytohormones.We also discuss the interaction of ripening-related and defense-related TFs with the Mediator transcription complex.As the ripening processes in climacteric and non-climacteric fruits share many similarities,these processes have broad applications across fruiting crops.Further research on the individual contributions of ERFs and other TFs will inform efforts to diminish disease susceptibility in ripe fruit,satisfy the growing demand for high-quality fruit and decrease food waste and related economic losses.

Annual periodicity of fruiting in temperate forests in Yakushima, Japan

Fruiting phenology, assessed by seed fall, in five warm- and cool-temperate forests on Yakushima Island, southern Japan, was studied for two years in one 50 m × 50 m plot and for four years in four 100 m ×50 m plots. The elevation of the plots ranged between 170 and 1200 m a.s.l. Seed fall phenology showed annual periodicity in all five plots. This was clear when assessed by the number of species but became less clear when assessed by the biomass of seed litter. Community-level annual periodicity was based on the prevalence of population-level annual periodicity and interspecific synchronization of the fruiting peak from autumn to winter. Fleshy fruits had peaks of seed fall in a wider range of months than non-fleshy fruits, since it is sometimes beneficial to bear fruit outside the community-level fruiting peaks in order to avoid interspecific competition for animal seed dispersers. No consistent effect of climatic factors on seed fall phenology was detected.

Fruit fall in five warm- and cool-temperate forests in Yakushima,Japan

Quantification of fruit fall is the only way to compare fruit food availability among different studies. This study aims to reveal the general characteristics of fruit fall in temperate forests, which should offer indispensable information for using fruit fall data as food availability for frugivores. Fruit fall in three warm-temperate and two cool-temperate forests on Yakushima, an island in southwestern Japan, were studied for two years in one cool-temperate plot of 50 m × 50 m in size and for four years in other plots of 100 m × 50 m in size. The elevations of the plots ranged 170-1200 m a.s.1. Fruit fall was highest in the lowland forests （599 and 564 DW kg·ha^-1·year^-1 and lowest in the mid-elevation forest （198 DW kg·ha^-1·year^-1）. Fleshy fruits and food-fruits for Japanese macaques constituted 3-37% and 4-87% of the total fruit fall, respectively. When only fleshy-fruit fall was compared, it was higher in the western lowland forest （222 DW kg.ha^-1.year^-1） than in any other forests （9-66 DW kg-ha^-1.year^-1）. The pulp of fleshy fruits, presumably the edible parts for frugivores, was only 1.1-12.7% of the total fi ait fall. The edible parts for Japanese macaques constituted 3-54% of the fruit fall, showing a high value where acorns are abundant. Half of the fruit-fall biomass consisted of only one or two non- fleshy-fruited species, which are usually dominant in many other temperate forests, such as Quercus and conifers. These variations agreed with the variations in occurrence of frugivorous （such as Japanese macaques）.

Conflicting selection pressures on seed size and germination caused by carnivorous seed dispersers

Plants produce nutritious,fleshy fruits that attract various animals to facilitate seed dispersal and recruitment dynamic.Species-specific differential selection of seed size by multiple frugivorous disperser assemblages may affect the subsequent germination of the ingested seeds.However,there is little empirical evidence supporting this association.In the present study,we documented conflicting selection pressures exerted on seed size and germination by five frugivorous carnivores on a mammal-dispersed pioneer tree,the date-plum persimmon(Diospyros lotus),in a subtropical forest.Fecal analyses revealed that these carnivores acted as primary seed dispersers of D.lotus.We also observed that seed sizes were selected based on body mass and were species-specific,confirming the“gape limitation”hypothesis;three small carnivores(the masked palm civet Paguma larvata,yellow-throated marten Martes flavigula,and Chinese ferret-badger Melogale moschata)significantly preferred to disperse smaller seeds in comparison with control seeds obtained directly from wild plants whereas the largest Asiatic black bears(Ursus thibetanus)ingested larger seeds.Seeds dispersed by medium-sized hog badgers(Arctonyx albogularis)were not significantly different from control seeds.However,regarding the influence of gut passage on seed germination,three arboreal dispersal agents(martens,civets,and bears)enhanced germination success whereas terrestrial species(ferret-badgers and hog badgers)inhibited the germination process compared with undigested control seeds.These conflicting selection pressures on seed size and germination may enhance the heterogeneity of germination dynamics and thus increase species fitness through diversification of the regeneration niche.Our results advance our understanding of seed dispersal mechanisms and have important implications for forest recruitment and ecosystem dynamics.

Beyond habitat structure: Landscape heterogeneity explains the monito del monte (Dromiciops gliroides) occurrence and behavior at habitats dominated by exotic trees

Habitat structure determines species occurrence and behavior.However,human activities are altering natural habitat structure,potentially hampering native species due to the loss of nesting cavities,shelter or movement pathways.The South American temperate rainforest is experiencing an accelerated loss and degradation,com­promising the persistence of many native species,and particularly of the monito del monte(Dromiciops gliroi­des Thomas,1894),an arboreal marsupial that plays a key role as seed disperser.Aiming to compare 2 contrast­ing habitats(a native forest and a transformed habitat composed of abandoned Eucalyptus plantations and native understory vegetation),we assessed D.gliroides’occurrence using camera traps and measured several structur­al features(e.g.shrub and bamboo cover,deadwood presence,moss abundance)at 100 camera locations.Com­plementarily,we used radio telemetry to assess its spatial ecology,aiming to depict a more complete scenario.Moss abundance was the only significant variable explaining D.gliroides occurrence between habitats,and no structural variable explained its occurrence at the transformed habitat.There were no differences in home range,core area or inter-individual overlapping.In the transformed habitats,tracked individuals used native and Eu­calyptus-associated vegetation types according to their abundance.Diurnal locations(and,hence,nesting sites)were located exclusively in native vegetation.The landscape heterogeneity resulting from the vicinity of native and Eucalyptus-associated vegetation likely explains D.gliroides occurrence better than the habitat structure it­self,as it may be use Eucalyptus-associated vegetation for feeding purposes but depend on native vegetation for nesting.