Project properties

Title Role of Arf3 in leafy head development: Cellular observation of leaf parenchyma in pakchoi overexpressing Arf3
Group Plant Breeding, Laboratory of
Project type thesis
Credits 24-39
Supervisor(s) Dr. Guusje Bonnema, XiaoXue Sun
Examiner(s) Dr. Guusje Bonnema
Contact info Guusje Bonnema,, tel. 0317-484028
Begin date 2020/02/01
End date 2022/12/01
Description Brassica species display enormous phenotypic variation, including leafy vegetables (heading Chinese cabbage, non-heading pakchoi), tuber crops (turnips) and oilcrops. Brassica genomes all have undergone a whole genome triplication (WGT) which facilitated this phenotype diversification. We study the so called domestication events. Which genomic mutations were needed to generate leafy heads? (cabbages, Chinese cabbages). Many different accessions were resequenced and bioinformatic analyses resulted in the identification of several selective sweeps (Nature Genetics 2016, doi:10.1038/ng.3634). Interestingly several candidate genes for leafy head formation are involved in leaf ab/ad-axial development. We study the role of BrARF3-1 (AUXIN Response Factor 3) in Chinese cabbage leafy head formation. A C terminal single amino acid change resulted in a clear leaf phenotype when overexpressed in Arabidopsis and in altered protein interactions. Overexpression of these different ARF3 alleles in Pakchoi resulted in plants with clear leafy heads, despite their typical pakchoi leaf morphology (long petioles). Clearly overexpression leads to increased leaf angles and leaf curvature. Previous studies showed that cellular organization of palisade and spongy parenchyma differs between non heading pakchoi and Chinese cabbage. We hypothesized that the looser organization of especially the spongy parenchyma facilitated leaf curvature in Chinese cabbage leaves, forming the leafy head.
In the proposed thesis, the student will use the microtome to generate leaf slices for phenotyping their cellular organization. This involves Chinese cabbage, pakchoi and pakchoi genotypes over expressing different Arf3 alleles. Leaf cellular data are compared to whole plant morphology to generate hypothesis on the genetic and molecular mechanisms of leafy head formation.
Used skills Microtome, microscope, statistical analysis
Requirements Breeding for stress tolerance and quality, advanced statistics, Preferably courses like MOB-30806 (regulation of plant development)