Leaf physiological and anatomical responses of two sympatric Paphiopedilum species to temperature

Paphiopedilum dianthum and P.micranthum are two endangered orchid species,with high ornamental and conservation values.They are sympatric species,but their leaf anatomical traits and flowering period have significant differences.However,it is unclear whether the differences in leaf structure of the two species will affect their adaptabilities to temperature.Here,we investigated the leaf photosynthetic,anatomical,and flowering traits of these two species at three sites with different temperatures(Kunming,16.7±0.2°C;Puer,17.7±0.2°C;Menglun,23.3±0.2°C)in southwest China.Compared with those at Puer and Kunming,the values of light-saturated photosynthetic rate(Pmax).stomatai conductance(gs),leaf thickness(LT),and stomatai density(SD)in both species were lower at Menglun.The values of Pmax,gs,仃,adaxial cuticle thickness(CTad)and SD in P.dianthum were higher than those of P.micranthum at the three sites.Compared with P.dianthum,there were no flowering plants of P.micranthum at Menglun.These results indicated that both species were less resistance to high temperature,and P.dianthum had a stronger adaptability to high-temperature than P.micranthum.Our findings can provide valuable information for the conservation and cultivation of Paphiopedilum species.

High-quality Cymbidium mannii genome and multifaceted regulation of crassulacean acid metabolism in epiphytes

Epiphytes with crassulacean acid metabolism(CAM)photosynthesis are widespread among vascular plants,and repeated evolution of CAM photosynthesis is a key innovation for micro-ecosystem adaptation.However,we lack a complete understanding of the molecular regulation of CAM photosynthesis in epiphytes.Here,we report a high-quality chromosome-level genome assembly of a CAM epiphyte,Cymbidium mannii(Orchidaceae).The 2.88-Gb orchid genome with a contig N50 of 22.7 Mb and 27192 annotated genes was organized into 20 pseudochromosomes,82.8%of which consisted of repetitive elements.Recent expansions of long terminal repeat retrotransposon families have made a major contribution to the evolution of genome size in Cymbidium orchids.We reveal a holistic scenario of molecular regulation of metabolic physiology using high-resolution transcriptomics,proteomics,and metabolomics data collected across a CAM diel cycle.Patterns of rhythmically oscillating metabolites,especially CAM-related products,reveal circadian rhythmicity in metabolite accumulation in epiphytes.Genomewide analysis of transcript and protein level regulation revealed phase shifts during the multifaceted regulation of circadian metabolism.Notably,we observed diurnal expression of several core CAM genes(especially bCA and PPC)that may be involved in temporal fixation of carbon sources.Our study provides a valuable resource for investigating post-transcription and translation scenarios in C.mannii,an Orchidaceae model for understanding the evolution of innovative traits in epiphytes.