The Cymbidium genome reveals the evolution of unique morphological traits

The marvelously diverse Orchidaceae constitutes the largest family of angiosperms.The genus Cymbidium in Orchidaceae is well known for its unique vegetation,floral morphology,and flower scent traits.Here,a chromosomescale assembly of the genome of Cymbidium ensifolium(Jianlan)is presented.Comparative genomic analysis showed that C.ensifolium has experienced two whole-genome duplication(WGD)events,the most recent of which was shared by all orchids,while the older event was the t event shared by most monocots.The results of MADS-box genes analysis provided support for establishing a unique gene model of orchid flower development regulation,and flower shape mutations in C.ensifolium were shown to be associated with the abnormal expression of MADS-box genes.The most abundant floral scent components identi fied included methyl jasmonate,acacia alcohol and linalool,and the genes involved in the floral scent component network of C.ensifolium were determined.Furthermore,the decreased expression of photosynthesis-antennae and photosynthesis metabolic pathway genes in leaves was shown to result in colorful striped leaves,while the increased expression of MADS-box genes in leaves led to perianth-like leaves.Our results provide fundamental insights into orchid evolution and diversi fication.

The GW2-WG1-OsbZIP47 pathway controls grain size and weight in rice

Regulation of seed size is a key strategy for improving crop yield and is also a basic biological question.However,the molecular mechanisms by which plants determine their seed size remain elusive.Here,we report that the GW2-WG1-OsbZIP47 regulatory module controls grain width and weight in rice.WG1,which encodes a glutaredoxin protein,promotes grain growth by increasing cell proliferation.Interestingly,WG1 interacts with the transcription factor OsbZIP47 and represses its transcriptional activity by associating with the transcriptional co-repressor ASP1,indicating that WG1 may act as an adaptor protein to recruit the transcriptional co-repressor.In contrary,OsbZIP47 restricts grain growth by decreasing cell proliferation.Further studies reveal that the E3 ubiquitin ligase GW2 ubiquitinates WG1 and targets it for degradation.Genetic analyses confirm that GW2,WG1,and OsbZIP47 function in a comm on pathway to control grain growth.Taken together,ourfindi ngs reveal a genetic and molecular framework for the control of grain size and weight by the GW2-WG1-OsbZIP47 regulatory module,providing new targets for improving seed size and weight in crops.