1. Fine genetic mapping and cloning of short hypocotyl (SH1) and long hypocotyl (LH1) genes. 2. Understand molecular mechanisms of regulation of hypocotyl elongation in cucumber. 3. Marker-assisted development short hypocotyl germplasm for cucumber breeding.
Objective 1: 1. We will use map-based cloning strategy to clone and characterize short hypocotyl (SH1) and long hypocotyl (LH1) genes for hypocotyl elongation. Near isogenic lines of each gene are being developed through marker-assisted backcrossing and phenotyping in both UV and UVB-free light conditions. Recombinants will be identified through flanking markers until the target gene region is narrowed down to less than 30kb. 2. Candidate genes in target regions will be identified and annotated. Objective 2: Functional characterization and understanding of regulatory network will be performed with the following experiments: 1. Quantitative PCR (qPCR) will be used to study expression dynamics in different tissues, development stages, and light conditions. 2. Allelic diversity of candidate genes will be examined in cucumber natural populations. 3. Genetic transformation of candidate genes in Arabidopsis. 4. Transcriptome profiling between of SH1 and LH1 near isogenic lines with RNA-Seq to reveal regulatory network. 5. Understand protein-protein interactions with the following techniques: year two hybrid (Y2H), pull-down assay, and BiFC (Bimolecular fluorescence complementation).