The main objective of my study is to understand the functional evolution of novel morphologies in correlation with changes in the molecular genetic mechanisms over a period of time. One can understand the source for the existence of a wide diversity of forms by uncovering the developmental processes behind it. The plant evolutionary developmental biology (evo-devo) emerged as a branch of study that aims at unraveling the molecular and genetic mechanisms responsible for the origin and diversification of plant morphologies during the process of evolution. Flowering plants or angiosperms are the most dominating terrestrial plant ecosystems and flowers are the reproductive structures responsible for their successful adaptation. The flower comprises of four different floral organs as sepals, petals, stamens, and carpels. Variations in these organs have contributed considerably to the diversification of angiosperms. Moreover, the origin and diversification of the female reproductive organ, the carpel, was a major contributor for the evolutionary success of flowering plants. Therefore, the functional analysis of carpel developmental genes in phylogenetic informative species is one way of deciphering plant development in an evolutionary context.The molecular mechanisms governing carpel development have been studied intensively in the core eudicot model species Arabidopsis thaliana (Arabidopsis) and to some extent in the monocot model plant Oryza sativa (Rice). However, such studies are limited in other evolutionary lineages due to lack of genetically tractable model systems. To overcome this obstacle, the basal eudicot plant, Eschscholzia californica (California poppy) has been established as a versatile developmental model species based on its phylogenetic position and its amenability to genetic manipulation. Hence, the molecular genetics of carpel development in California poppy helps in bridging the evolutionary gap between monocots and higher eudicots. AGAMOUS (AG) is one of the important carpel developmental genes involved in specifying stamen and carpel identity in A. thaliana. In E. californica, there are two AG homologs, EScaAG1 and EScaAG2 which exhibit high sequence similarity at both nucleotide and protein levels. However, expression analyses through real-time qRT-PCR have shown that EScaAG2 is being expressed stronger in the inner stamen whorls and EScaAG1 transcripts are more abundant in the central carpels. Furthermore, downregulation of EScaAG1 through Virus-induced gene silencing (VIGS) resulted in the homeotic conversion of outer, peripheral whorls of stamens into petals and VIGS-EScaAG2 led to the homeotic transformation of inner and central whorls of stamens into petals. Additionally, functional analysis of both EScaAG genes through VIGS has resulted in the homeotic conversion of carpels into petal-like structures. According to the ABCE model of floral organ specification, petal identity requires the presence of the floral homeotic B function genes. The results of the present study have shown that the expression of a subset of B-function genes extends into the central fourth whorl when the C function is reduced. This suggests a phenomenon of B function gene regulation by the floral homeotic C function gene EScaAG2, a new functional domain of C class genes that has not been uncovered in any other model species.In the second project, Agrobacterium tumefaciens mediated stable genetic transformation was attempted for E. californica with a special emphasis on establishing a reproducible transgenic regeneration system. As a new source of explant tissue that was used as a starter culture, unripe seeds were selected and the protocol was optimized to produce embryogenic calli with efficient somatic embryogenesis and subsequent plant regeneration. The unripe seeds collected during a timeframe of 22-24 days after anthesis (DAA) proved to be suitable to induce callus production. Furthermore, the addition of sucrose in all the tissue culture growing media enhanced the efficiency of subsequent somatic embryogenesis, plantlet regeneration and root induction from the unripe seed sources.
Verknüpfung zu Publikationen oder weiteren Datensätzen
