Functional genomics of photosynthetic genes in sugarcane

Resumo

Sugarcane (Saccharum officinarum) is one of the most important feedstock sources for biofuel. In Brazil, sugarcane has been a prominent cultivated species undergoing accelerated expansion. This crop has launched Brazil as the major and most relevant country for exporting ethanol, as well as it became an important source of world bioenergy. In order to sustain and develop this enlarging agricultural and commercial sector, in a long-term, it becomes mandatory a continued quick release of increasingly productive sugarcane cultivars carrying specific advantageous traits, including increased sucrose content. Adversely, the breeding of sugarcane has been naturally limited by its low fertility, complex genome, narrow genetic basis, and long periods of 12 to 15 years to create a new variety. The development of efficient systems of molecular biology and genetic transformation are fundamental, and often the only way, to rapidly introducing new valuable agronomic and commercial traits into sugarcane elite germplasm. Increase of sucrose content in elite sugarcane cultivars may be a main point to be addressed by using genetic transformation, and is directly dependent of increasing photosynthetic efficiency. The vast majority of photosynthetic proteins is nucleus-encoded and require N-terminal presequences, named chloroplast transit peptides, to target them to the chloroplast. About 2100 to 3600 distinct chloroplast proteins are nuclear-encoded, while about 100 to 120 are encoded by the organelle genome. The present project aims to develop efficient methods of sugarcane in vitro culture as well as methods of nuclear and chloroplast genetic transformation, applying them to modify photosynthetic genes in order to incorporate new photosynthetic traits in already productive Brazilian cultivars. The sugarcane photosynthetic efficiency is expected to be improved upon manipulation of photosynthetic genes (i.e. ribulose-1,5-bisphosphate carboxylase/oxygenase, phosphoenolpyruvate carboxylase, carbonic anhydrase) generating novel knowledge in this research field as well as leading to increased synthesis of triose phosphates and, ultimately, increased sucrose content in the transgenic cultivars. (AU)