RESUMEN
Chrysolaena obovata (Less.) Dematt., previously named Vernonia herbacea, is an Asteraceae native to the Cerrado which accumulates about 80% of the rhizophore dry mass as inulin-type fructans. Considering its high inulin production and the wide application of fructans, a protocol for C. obovata in vitro culture was recently established. Carbohydrates are essential for in vitro growth and development of plants and can also act as signaling molecules involved in cellular adjustments and metabolic regulation. This work aimed to evaluate the effect of different sources of carbohydrate on fructan metabolism in plants grown in vitro. For this purpose, C. obovata plants cultivated in vitro were submitted to carbon deprivation and transferred to MS medium supplemented with sucrose, glucose or fructose. Following, their fructan composition and activity and expression of genes encoding enzymes for fructan synthesis (1-SST and 1-FFT) and degradation (1-FEH) were evaluated. For qRT-PCR analysis partial cDNA sequences corresponding to two different C. obovata genes, 1-SST and 1-FFT, were isolated. As expected, C. obovata sequences showed highest sequence identity to other Asteraceae 1-SST and 1-FFT, than to Poaceae related proteins. A carbon deficit treatment stimulated the transcription of the gene 1-FEH and inhibited 1-SST and 1-FFT and carbohydrate supplementation promoted reversal of the expression profile of these genes. With the exception of 1-FFT, a positive correlation between enzyme activity and gene expression was observed. The overall results indicate that sucrose, fructose and glucose act similarly on fructan metabolism and that 1-FEH and 1-SST are transcriptionally regulated by sugar in this species. Cultivation of plants in increasing sucrose concentrations stimulated synthesis and inhibited fructan mobilization, and induced a distinct pattern of enzyme activity for 1-SST and 1-FFT, indicating the existence of a mechanism for differential regulation between them.
RESUMEN
We report on the production and evaluation of passionflower transgenic lines for resistance to Cowpea aphid borne mosaic virus (CABMV). Genetic transformation was done using Agrobacterium tumefaciens and transgene integration was confirmed by Southern blot analyses, resulting in nine transgenic lines for 'IAC 275' and three for 'IAC 277'. Transgenic lines were clonally propagated and evaluated for resistance to CABMV. After the third inoculation, under higher inoculum pressure, only propagated plants of the transgenic line T16 remained asymptomatic, indicating a high resistance to infection with CABMV. This transgenic line was self-pollinated and the R1 generation was evaluated together with the R1 generation of another resistant transgenic line (T2) identified previously. Plants were inoculated with CABMV by means of viruliferous Myzus nicotianae. All 524 T2R1 plants became infected, whereas 13 of 279 T16R1 remained asymptomatic after four successive inoculations. A T16R2 generation was obtained and plants were inoculated with CABMV mechanically or by aphids. After successive inoculations, 118 of 258 plants were symptomless, suggesting that the resistance to CABMV was maintained in the plant genome as the homozygous condition was achieved. Five selected resistant T16R2 plants which contained the capsid protein gene are being crossed for further analyses.