Candidate gene analysis of watermelon stripe pattern locus ClSP ongoing recombination suppression.

KEY MESSAGE: Using two segregating population, watermelon stripe pattern underlying gene ClSP was delimited to a 611.78 Kb region, consisting of four discrete haploblocks and ongoing recombination suppression. Stripe pattern is an important commodity trait in watermelon, displaying diverse types. In this study, two segregating populations were generated for genetic mapping the single dominant locus ClSP, which was finally delimited to a 611.78 Kb interval with suppression of recombination. According to polymorphism sites detected among genotypes, four discrete haploblocks were characterized in this target region. Based on reference genomes, 81 predicted genes were annotated in the ClSP interval, including seven transcription factors namely as candidate No1-No7. Meanwhile, the ortholog gene of cucumber ist responsible for the irregular stripes was considered as candidate No8. Strikingly, gene structures of No1-No5 completely varied from their reference descriptions and subsequently re-annotated. For instance, the original adjacent distribution candidates No2 and No3 were re-annotated as No2_3, while No4 and No5 were integrated as No4_5. Sequence analysis demonstrated the third polymorphism in CDS of re-annotated No4_5 resulting in truncated proteins in non-stripe plants. Furthermore, only No4_5 was down-regulated in light green stripes relative to dark green stripes. Transcriptome analysis identified 356 DEGs between dark green striped and light green striped peels, with genes involved in photosynthesis and chloroplast development down-regulated in light green stripes but calcium ion binding related genes up-regulated. Additionally, 38 DEGs were annotated as transcription factors, with the majority up-regulated in light green stripes, such as ERFs and WRKYs. This study not only contributes to a better understanding of the molecular mechanisms underlying watermelon stripe development, but also provides new insights into the genomic structure of ClSP locus and valuable candidates.

Wireless optoelectronic photometers for monitoring neuronal dynamics in the deep brain.

Capabilities for recording neural activity in behaving mammals have greatly expanded our understanding of brain function. Some of the most sophisticated approaches use light delivered by an implanted fiber-optic cable to optically excite genetically encoded calcium indicators and to record the resulting changes in fluorescence. Physical constraints induced by the cables and the bulk, size, and weight of the associated fixtures complicate studies on natural behaviors, including social interactions and movements in environments that include obstacles, housings, and other complex features. Here, we introduce a wireless, injectable fluorescence photometer that integrates a miniaturized light source and a photodetector on a flexible, needle-shaped polymer support, suitable for injection into the deep brain at sites of interest. The ultrathin geometry and compliant mechanics of these probes allow minimally invasive implantation and stable chronic operation. In vivo studies in freely moving animals demonstrate that this technology allows high-fidelity recording of calcium fluorescence in the deep brain, with measurement characteristics that match or exceed those associated with fiber photometry systems. The resulting capabilities in optical recordings of neuronal dynamics in untethered, freely moving animals have potential for widespread applications in neuroscience research.

A point mutation resulting in a 13 bp deletion in the coding sequence of Cldf leads to a GA-deficient dwarf phenotype in watermelon.

The dwarf architecture is an important and valuable agronomic trait in watermelon breeding and has the potential to increase fruit yield and reduce labor cost in crop cultivation. However, the molecular basis for dwarfism in watermelon remains largely unknown. In this study, a recessive dwarf allele (designated as Cldf (Citrullus lanatus dwarfism)) was fine mapped in a 32.88 kb region on chromosome 09 using F2 segregation populations derived from reciprocal crossing of a normal line M08 and a dwarf line N21. Gene annotation of the corresponding region revealed that the Cla015407 gene encoding a gibberellin 3ß-hydroxylase functions as the best possible candidate gene for Cldf. Sequence analysis showed that the fourth polymorphism site (a G to A point mutation) at the 3' AG splice receptor site of the intron leads to a 13 bp deletion in the coding sequence of Cldf in dwarf line N21 and thus results in a truncated protein lacking the conserved domain for binding 2-oxoglutarate. In addition, the dwarf phenotype of Cldf could be rescued by exogenous GA3 application. Phylogenetic analysis suggested that the small multigene family GA3ox (GA3 oxidase) in cucurbit species may originate from three ancient lineages in Cucurbitaceae. All these data support the conclusion that Cldf is a GA-deficient mutant, which together with the cosegregated marker can be used for breeding new dwarf cultivars.