Differential rubisco content and photosynthetic efficiency of rol gene integrated Vinca minor transgenic plant: Correlating factors associated with morpho-anatomical changes, gene expression and alkaloid productivity.

Transgenic plants obtained from a hairy root line (PVG) of Vinca minor were characterized in relation to terpenoid indole alkaloids (TIAs) pathway gene expression and vincamine production. The hairy roots formed callus with green nodular protuberances when transferred onto agar-gelled MS medium containing 3.0mg/l zeatin. These meristematic zones developed into shoot buds on medium with 1.0mg/l 2, 4-dichlorophenoxyacetic acid and 40mg/l ascorbic acid. These shoot buds subsequently formed rooted plants when shifted onto a hormone-free MS medium with 6% sucrose. Transgenic nature of the plants was confirmed by the presence of rol genes of the Ri plasmid in them. The transgenic plants (TP) had elongated internodes and a highly proliferating root system. During glass house cultivation TP consistently exhibited slower growth rate, low chlorophyll content (1.02±0.08mg/gm fr. wt.), reduced carbon exchange rate (2.67±0.16µmolm-2s-1), less transpiration rate (2.30±0.20mmolm-2 s-1) and poor stomatal conductance (2.21±0.04mmolm-2 s-1) when compared with non-transgenic population. The activity of rubisco enzyme in the leaves of TP was nearly two folds less in comparison to non-transgenic controls (1.80milliunitsml-1mgprotein-1 against 3.61milliunits ml-1mgprotein-1, respectively). Anatomically, the TP had a distinct tetarch arrangement of vascular bundles in their stem and roots against a typical ployarched pattern in the non-transgenic plants. Significantly, the transgenic plants accumulated 35% higher amount of total TIAs (3.10±0.21% dry wt.) along with a 0.03% dry wt. content of its vasodilatory and nootropic alkaloid vincamine in their leaves. Higher productivity of alkaloids in TP was corroborated with more than four (RQ=4.60±0.30) and five (RQ=5.20±0.70) times over-expression of TIAs pathway genes tryptophan decarboxylase (TDC) and strictosidine synthase (STR) that are responsible for pushing the metabolic flux towards TIAs synthesis in this medicinal herb.

A double-flowered variety of lesser periwinkle (Vinca minor fl. pl.) that has persisted in the wild for more than 160 years.

BACKGROUND AND AIMS: Homeotic transitions are usually dismissed by population geneticists as credible modes of evolution due to their assumed negative impact on fitness. However, several lines of evidence suggest that such changes in organ identity have played an important role during the origin and subsequent evolution of the angiosperm flower. Better understanding of the performance of wild populations of floral homeotic varieties should help to clarify the evolutionary potential of homeotic mutants. Wild populations of plants with changes in floral symmetry, or with reproductive organs replacing perianth organs or sepals replacing petals have already been documented. However, although double-flowered varieties are quite popular as ornamental and garden plants, they are rarely found in the wild and, if they are, usually occur only as rare mutant individuals, probably because of their low fitness relative to the wild-type. We therefore investigated a double-flowered variety of lesser periwinkle, Vinca minor flore pleno (fl. pl.), that is reported to have existed in the wild for at least 160 years. To assess the merits of this plant as a new model system for investigations on the evolutionary potential of double-flowered varieties we explored the morphological details and distribution of the mutant phenotype. METHODS: The floral morphology of the double-flowered variety and of a nearby population of wild-type plants was investigated by means of visual inspection and light microscopy of flowers, the latter involving dissected or sectioned floral organs. KEY RESULTS: The double-flowered variety was found in several patches covering dozens of square metres in a forest within the city limits of Jena (Germany). It appears to produce fewer flowers than the wild-type, and its flowers are purple rather than blue. Most sepals in the first floral whorl resemble those in the wild-type, although occasionally one sepal is broadened and twisted. The structure of second-whorl petals is very similar to that of the wild-type, but their number per flower is more variable. The double-flowered character is due to partial or complete transformation of stamens in the third whorl into petaloid organs. Occasionally, 'flowers within flowers' also develop on elongated pedicels in the double-flowered variety. CONCLUSIONS: The flowers of V. minor fl. pl. show meristic as well as homeotic changes, and occasionally other developmental abnormalities such as mis-shaped sepals or loss of floral determinacy. V. minor fl. pl. thus adds to a growing list of natural floral homeotic varieties that have established persistent populations in the wild. Our case study documents that even mutant varieties that have reproductive organs partially transformed into perianth organs can persist in the wild for centuries. This finding makes it at least conceivable that even double-flowered varieties have the potential to establish new evolutionary lineages, and hence may contribute to macroevolutionary transitions and cladogenesis.