ABSTRACT
Abstract Bauhinia monandra Kurz (Fabaceae) is an ornamental leguminous tree from Africa. Its leaf has been proven to be hypoglycaemic, and are a source of lecithin BmoLL, providing this species with great medicinal potential. Curiously, there are no reports of the anatomical description of the leaf of this species. The present work aimed at describing the leaf anatomy of B. monandra, and make histochemical inferences. To this end, anatomical procedures in light and scanning electron microscopy were performed from different parts of the leaves of plants growing in the state of Bahia, Brazil. The leaf is amphistomatous. It possesses papillate epidermis, nonglandular and navicular trichomes, and the mesophyll is dorsiventral. The central vein is distinct from the others of the first degree. The first, second, and third-degree veins possess thick fibre bundles with associated monocrystals. The other veins are a little fibrous and excessively reduced. The petiole vascularisation consists of circularly arranged collateral bundles, plus two accessory bundles. The pulvinus have a wide parenchymatic cortex with abundant druses and vascularisation restricted to the central region, surrounded by a crystalline sheath and by a starch sheath. The motile cushion has the vascular bundles arranged in series. Associated with the phloem from the pulvinus vascular bundles and the motile apparatus, occur non-lignified septate fibres that confer flexibility to these organs. The absence of lateral projections and the arrangement of vascular bundles in the petiole was the most distinctive anatomical features and of the greatest taxonomic potential observed in the leaf of B. monandra.
ABSTRACT
Background: Osmanthus fragrans is an important ornamental tree and has been widely planted in China because of its pleasant aroma, which is mainly due to terpenes. The monoterpenoid and sesquiterpenoid metabolic pathways of sweet osmanthus have been well studied. However, these studies were mainly focused on volatile small molecule compounds. The molecular regulation mechanism of synthesis of large molecule compounds (triterpenoids) remains unclear. Squalene synthase (SQS), squalene epoxidase (SQE), and beta-amyrin synthase (BETA-AS) are three critical enzymes of the triterpenoid biosynthesis pathway. Results: In this study, the full-length cDNA and gDNA sequences of OfSQS, OfSQE, and OfBETA-AS were isolated from sweet osmanthus. Phylogenetic analysis suggested that OfSQS and OfSQE had the closest relationship with Sesamum indicum, and OfBETA-AS sequence shared the highest similarity of 99% with that of Olea europaea. The qRT-PCR analysis revealed that the three genes were highly expressed in flowers, especially OfSQE and OfBETA-AS, which were predominantly expressed in the flowers of both "Boye" and "Rixiang" cultivars, suggesting that they might play important roles in the accumulation of triterpenoids in flowers of O. fragrans. Furthermore, the expression of OfBETA-AS in the two cultivars was significantly different during all the five flowering stages; this suggested that OfBETA-AS may be the critical gene for the differences in the accumulation of triterpenoids. Conclusion: The evidence indicates that OfBETA-AS could be the key gene in the triterpenoid synthesis pathway, and it could also be used as a critical gene resource in the synthesis of essential oils by using bioengineered bacteria.