Effects of shade on the development and sugar metabolism of coffee (Coffea arabica L.) fruits.

Coffee fruits grown in shade are characterized by larger bean size than those grown under full-sun conditions. The present study assessed the effects of shade on bean characteristics and sugar metabolism by analyzing tissue development, sugar contents, activities of sucrose metabolizing enzymes and expression of sucrose synthase-encoding genes in fruits of coffee (Coffea arabica L.) plants submitted to full-sun (FS) and shade (SH) conditions. Evolution of tissue fresh weights measured in fruits collected regularly from flowering to maturation indicated that this increase is due to greater development of the perisperm tissue in the shade. The effects of light regime on sucrose and reducing sugar (glucose and fructose) contents were studied in fresh and dry coffee beans. Shade led to a significant reduction in sucrose content and to an increase in reducing sugars. In pericarp and perisperm tissues, higher activities of sucrose synthase (EC 2.4.1.13) and sucrose-phosphate synthase (SPS: EC 2.4.1.14) were detected at maturation in the shade compared with full sun. These two enzymes also had higher peaks of activities in developing endosperm under shade than in full sun. It was also noted that shade modified the expression of SUS-encoding genes in coffee beans; CaSUS2 gene transcripts levels were higher in SH than in FS. As no sucrose increase accompanied these changes, this suggests that sucrose metabolism was redirected to other metabolic pathways that need to be identified.

Biochemical and genomic analysis of sucrose metabolism during coffee (Coffea arabica) fruit development.

Sucrose metabolism and the role of sucrose synthase were investigated in the fruit tissues (pericarp, perisperm, and endosperm) of Coffea arabica during development. Acid invertase, sucrose phosphate synthase, and sucrose synthase activities were monitored and compared with the levels of sucrose and reducing sugars. Among these enzymes, sucrose synthase showed the highest activities during the last stage of endosperm and pericarp development and this activity paralleled closely the accumulation of sucrose in these tissues at this stage. Carbon partitioning in fruits was studied by pulse-chase experiments with (14)C-sugars and revealed high rates of sucrose turnover in perisperm and endosperm tissues. Additional feeding experiments with (14)CO(2) showed that leaf photosynthesis contributed more to seed development than the pericarp in terms of photosynthate supply to the endosperm. Sugar analysis, feeding experiments, and histological studies indicated that the perisperm plays an important role in this downloading process. It was observed that the perisperm presents a transient accumulation of starch which is degraded as the seed develops. Two full-length cDNAs (CaSUS1 and CaSUS2) and the complete gene sequence of the latter were also isolated. They encode sucrose synthase isoforms that are phylogenetically distinct, indicating their involvement in different physiological functions during cherry development. Contrasting expression patterns were observed for CaSUS1 and CaSUS2 in perisperm, endosperm, and pericarp tissues: CaSUS1 mRNAs accumulated mainly during the early development of perisperm and endosperm, as well as during pericarp growing phases, whereas those of CaSUS2 paralleled sucrose synthase activity in the last weeks of pericarp and endosperm development. Taken together, these results indicate that sucrose synthase plays an important role in sugar metabolism during sucrose accumulation in the coffee fruit.

Propagação in vivo e invitro de Cissus sicyoides, uma planta medicinal

The study of the propagation of species used in common medicine has intensified in the last few years due to the increasing investment in research for the discovery of new pharmaceuticals and utilization of phytotherapy as an alternative. The objective of this study was in vivo and in vitro propagation (establishment and multiplication) of Cissus sicyoides. Greenhouse plants furnished 10 and 20 cm long cuttings which were placed for two hours in 0, 80 or 160 mg/l of IBA, with or without sucrose and boric acid. For the in vitro establishment, the nodal segments were sterilized, 10 mm sections were inoculated in a solid culture (MS), and supplemented with kinetin, ANA and BAP. For the multiplication in vitro, 10 mm nodal segments were inoculated in a solid culture (MS), supplemented with the following interactions: BAP x ANA and ANA x kinetin. The 10 cm long cuttings presented good rooting when treated with 160 mg/l of AIB. In vitro the explants were established and multiplied better in a culture supplemented with 4.64 of kinetin and 2.7 of ANA, which promoted greater induction of buds, greater height and absence of callus formation at the base of plantlets.

O estudo da propagação de espécies utilizadas na medicina popular tem sido intensificado nos últimos anos devido ao crescente investimento em pesquisas para a descoberta de novos fármacos e da utilização da fitoterapia como um meio alternativo. O objetivo do trabalho foi a propagação in vivo e in vitro (estabelecimento e multiplicação) de Cissus sicyoides. Plantas mantidas em casa de vegetação forneceram estacas com 10 e 20 cm de comprimento, as quais foram tratadas com 0, 80 ou 160 mg/l de AIB, com ou sem sacarose + ácido bórico, por duas horas. Para o estabelecimento in vitro, após desinfestação, segmentos nodais com 10 mm de comprimento foram inoculados em meio de cultura sólido (MS), com diferentes concentrações de cinetina, BAP e ANA. Para a multiplicação in vitro, segmentos nodais com 10 mm foram inoculados em meio MS, suplementado com diferentes concentrações de BAP e ANA, e ANA e cinetina. Na propagação in vivo as estacas com 10 cm de comprimento apresentaram maior eficiência no enraizamento quando tratadas com 160 mg/l de AIB. In vitro os explantes foram melhor estabelecidos e multiplicados em meio de cultura suplementado com cinetina e ANA, que proporcionaram maior indução de gemas, crescimento em altura e ausência de calos na base das plântulas.