Transcriptomics of Sugarcane Osmoprotectants Under Drought

Abstract

Sugarcane (Saccharum spp.) is an alogamous plant from the Poaceae family and the Andropogoneae tribe (Daniels & Roach, 1987). This crop covers more than 23 million hectares worldwide, representing about 0.5 % of the total global area used for agriculture, with a production of 1.6 billion metric tons of crushable stems (FAOSTAT, 2009). Brazil is the world’s largest producer, contributing with two-thirds of total sugar production about 31 million tons per year of which 19.5 million tons are exported (UNICA, 2009). Sugarcane, its derivatives and by products have received great attention, due to their multiple uses, with emphasis on the ethanol production, representing an important renewable biofuel source. It has been estimated that sugarcane ethanol fuel may replace up to 10.0 % of the world’s refined petroleum products consumption in the next 15 to 20 years (Goldemberg, 2007). Despite its importance and similarity to other important agronomic crops, the sugarcane production has been adversely influenced by many environmental factors such as harsh climate and soil conditions. Abiotic stresses are among the main causes of losses in the productivity of the major crops worldwide (Bray et al., 2000), a scenario where drought figures as the most significant stress, causing negative impacts on crop adaptation and productivity. Besides, this condition can exacerbate the effect of other stresses (biotic or abiotic) to which the plants may be submitted. Although breeding activities have provided significant progress for the understanding of the physiological and molecular responses of plants to water deficit, there is still a large gap between yields in optimal and stressful conditions (Cattivelli et al., 2008). Essays regarding plant responses to drought stress have been published applying technologies of functional genomics (Wang et al., 2011). These evaluations provided important insights into molecular and biochemical mechanisms in the study of drought tolerance in various crops and model species. Plants are able to ‘‘perceive’’ the external stimuli by multiple sensors, recognizing adverse situations and invoking signal transduction cascades and consequently secondary messengers, activating stress responsive genes (Grennan, 2006), resulting in both molecular and physiological responses. Among the mechanisms developed by plants to face the adverse conditions generated under drought, the accumulation of osmoprotectants compounds are often recognized as a mitigation mechanism of the negative consequences of water deficit (Choluj et al., 2008).