Molecular characterisation of flowering genes in Pongamia Pinnata

Abstract

Pongamia pinnatan(Pongamia) is a multipurpose treenthat has been used traditionally for medicine, green manure, insecticide, fuel and also a source of timber. It is an indigenous plant to the Indian subcontinent and Southeast Asia, and has been successfully introduced to Northern Australia, New Zealand and several other countries with humid tropical lowlands. Recently, Pongamianhas attracted interest as one of the alternative feedstock for biodiesel productions due to its ability to produce seeds with high oil content. The fatty acid methyl ester (FAME) composition of Pongamia met the biodiesel specification standards of USA (ASTMD 6751), Germany (DIN 51606) and European Standard Organisation (EN 14214), and is considered as one of the most suitable sources of biodiesel. Despite the positive attributes described above, Pongamia is not a domesticated species and further research is required for the selection of elite cultivars with desirable traits optimal for large scale production of Pongamia oil. In addition, limited information is currently available regarding the flowering mechanism of Pongamia at the molecular level that could provide the platform for the development of oil-rich seeds.nThe aim of this thesis is to provide insight and increase the understanding of the genetic network that leads to flowering in Pongamia. Based on large phenotypic diversity of Pongamia, this information could subsequently be used to determine and select traits with unique flowering time that will allow a harvesting window, where harvesting process will not clash with flowering.nThe first objective of this project is to identify, isolate and characterise the candidate genes that regulate flowering time in Pongamia. This was achieved using molecular biology techniques and bioinformatic approaches based on the information available on flowering mechanisms of Arabidopsis and soybean in the literature.The second objective of this project is to determine the expression pattern of isolated genes during flowering onset. This was achieved through transcriptome methodologies such as RT-PCR and qRT-PCR. The third objective of this project is to investigate the genetic variety of Pongamia. This was achieved through Single Nucleotide Polymorphism (SNPs) analysis and its correlation with the late flowering phenotype of Pongamia.nPpCOL-1nandnPpPHYBnare the two genes that were investigated in this thesis. The orthologue genes ofnPpCOL-1nandnPpPHYBnare involved in the flowering regulation of the annual plant Arabidopsis. Since Arabidopsis and Pongamia are both long day plants, it is postulated that these genes might play a role in the flowering time control in Pongamia.nPpCOL-1nandPpPHYBnwere successfully isolated, characterised and compared to their respective orthologue genes in Arabidopsis, Soybean and Medicago. It was found that the amino acid residues within the domain regions in these genes are highly conserved in Pongamia. Interestingly, there were no significant differences in the expression patterns ofnPpCOL-1nandnPpPHYBnin plants under long day or short day conditions. Their genetic diversity were also utilised to study the correlation of SNPs in the gene with their flowering phenotype. These results provide insight into the possible roles ofnPpCOL-1nandnPpPHYBnin flowering regulation of Pongamia.nIn summary, the outcome of this project demonstrates the many factors that are associated in flowering time control in Pongamia, which is suggested to involve highly conserved genes. However, further studies especially on the functional aspect of these genes will need to be done to increase our understanding of their roles in Pongamia.nIt could be useful in creating a molecular platform for traits selection of flowering time in the future. Based on the large phenotypic diversity of Pongamia, this information could subsequently be used to determine the selection of traits with unique flowering time that will allow a harvesting window, where the harvesting process will not clash with flowering and subsequently ensuring the optimum yield of seeds favourable for biofuel production.n