Melon short internode(CmSi)encodes an ERECTA-like receptor kinase regulating stem elongation through auxin signaling

Plant height is one of the most important agronomic traits that directly determines plant architecture,and compact or dwarf plants can allow for increased planting density and land utilization as well as increased lodging resistance and economic yield.At least four dwarf/semidwarf genes have been identified in different melon varieties,but none of them have been cloned,and little is known about the molecular mechanisms underlying internode elongation in melon.Here,we report map-based cloning and functional characterization of the first semidwarf gene short internode(Cmsi)in melon,which encodes an ERECTA-like receptor kinase regulating internode elongation.Spatial-temporal expression analyses revealed that CmSI exhibited high expression in the vascular bundle of the main stem during internode elongation.The expression level of CmSI was positively correlated with stem length in the different melon varieties examined.Ectopic expression of CmSI in Arabidopsis and cucumber suggested CmSI as a positive regulator of internode elongation in both species.Phytohormone quantitation and transcriptome analysis showed that the auxin content and the expression levels of a number of genes involved in the auxin signaling pathway were altered in the semidwarf mutant,including several well-known auxin transporters,such as members of the ABCB family and PINFORMED genes.A melon polar auxin transport protein CmPIN2 was identified by protein–protein interaction assay as physically interacting with CmSI to modulate auxin signaling.Thus,CmSI functions in an auxin-dependent regulatory pathway to control internode elongation in melon.Our findings revealed that the ERECTA family gene CmSI regulates stem elongation in melon through auxin signaling,which can directly affect polar auxin transport.

Molecular cytogenetic map visualizes the heterozygotic genome and identifies translocation chromosomes in Citrus sinensis

Citrus sinensis is the most cultivated and economically valuable Citrus species in the world,whose genome has been assembled by three generation sequencings.However,chromosome recognition remains a problem due to the small size of chromosomes,and difficulty in differentiating between pseudo and real chromosomes because of a highly heterozygous genome.Here,we employ fluorescence in situ hybridization(FISH)with 9 chromosome painting probes,30 oligo pools,and 8 repetitive sequences to visualize 18 chromosomes.Then,we develop an approach to identify each chromosome in one cell through single experiment of oligo-FISH and Chromoycin A3(CMA)staining.By this approach,we construct a high-resolution molecular cytogenetic map containing the physical positions of CMA banding and 38 sequences of FISH including centromere regions,which enables us to visualize significant differences between homologous chromosomes.Based on the map,we locate several highly repetitive sequences on chromosomes and estimate sizes and copy numbers of each site.In particular,we discover the translocation regions of chromosomes 4 and 9 in C.sinensis“Valencia.”The high-resolution molecular cytogenetic map will help improve understanding of sweet orange genome assembly and also provide a fundamental reference for investigating chromosome evolution and chromosome engineering for genetic improvement in Citrus.