IDENTIFICATION OF MICRORNA FAMILIES EXPRESSED IN SUGARCANE LEAVES SUBJECTED TO DROUGHT STRESS AND THE TARGETS THEREOF.

MicroRNA families are important regulators of plant resistance to diverse stressors, but the miRNA families expressed in response to drought, and the levels thereof, in sugarcane (an important commercial source of both sugar and biofuel) remain poorly understood. In the present study, we determined the expression profile of miRNA families synthesized by leaves of the drought-resistant cultivar ROC22 stressed by addition of PEG to the growth substrate. Totals of 23 conserved miRNA families and 34 new miRNA families were identified, and 438 putative target genes of 44 miRNA families were described. Expression analysis revealed that 11 miRNA families were differentially expressed in control and drought-exposed plants. Of these, nine families were up-regulated and two down-regulated. The potential targets of the 11 miRNA families were genes associated with plant growth and stress resistance, specifically SPBP, MYB, the AGO1-like gene, NCBP, BCP, CPI, and LSG. With the exceptions of SPBP, NCBP and BCP, the other genes were down-regulated in response to drought stress. Our preliminary identification of 11 relevant miRNA families expressed by ROC22, and their targets, suggest that these miRNA families may regulate the response to drought stress and forms a basis for planned future work. The other new miRNA families identified, along with their targets, may exert novel effects on various metabolic pathways relevant to sugarcane growth and development. [ABSTRACT FROM AUTHOR]