Disclosed are compositions, reagents, methods, assays, and kits for quantitative and sensitive detection of target ribonucleic acid (RNA) sequences, particularly target RNA sequences that contain RNA spliced sites, hairpin stem-loops or other topological configurations of RNA secondary, tertiary, and quaternary structure, as well as linear RNA sequences. In some embodiments, fluorogenic modified-backbone oligonucleotide probes are employed for specific sequence hybridization across the target site, followed by chemical autoligation to produce a fluorescent molecule within the ligated probes. The autoligation detection reaction is performed isothermally or through thermocycling.