A method for amplifying a nucleic acid template comprising: reverse transcribing a single-stranded RNA to produce a linear double-stranded nucleic acid comprising two separate complementary strands: forming a circular strand comprising a first polynucleotide adaptor and a second polynucleotide adaptor and the two complementary strands, wherein each adaptor comprises a single nucleic acid strand which contains a nucleotide sequence of one strand of a restriction enzyme recognition sequence; annealing the circular strand of step with a first polynucleotide primer and synthesizing an extension product of the first primer; annealing the extension product of the first primer of step with a second polynucleotide primer and synthesizing an extension product of the second primer, wherein the extension product of the second primer is complementary to the extension product of the first primer; producing a new double-stranded nucleic acid comprising at least a portion of the extension product of the first primer and at least a portion of the extension product of the second primer and a full double-stranded restriction enzyme recognition sequence corresponding to the sequence of the one strand of the restriction enzyme recognition sequence of step; cleaving the new double-stranded nucleic acid from step with a restriction enzyme; and forming two or more shorter double-stranded nucleic acids, at least two of which comprise at least a portion of a copy of the linear double-stranded nucleic acid of step, thereby amplifying the linear double-stranded nucleic acid; wherein steps to are performed in a reaction mixture under isothermal conditions, and wherein the reaction mixture comprises: (i) the single-stranded RNA; (ii) a reverse transcriptase; (iii) the first polynucleotide adaptor and the second polynucleotide adaptor; (iv) the first polynucleotide primer and the second polynucleotide primer; (v) a ligase; (vi) a polymerase; and (vii) the restriction enzyme. reverse transcribing a single-stranded RNA to produce a linear double-stranded nucleic acid comprising two separate complementary strands: forming a circular strand comprising a first polynucleotide adaptor and a second polynucleotide adaptor and the two complementary strands, wherein each adaptor comprises a single nucleic acid strand which contains a nucleotide sequence of one strand of a restriction enzyme recognition sequence; annealing the circular strand of step with a first polynucleotide primer and synthesizing an extension product of the first primer; annealing the extension product of the first primer of step with a second polynucleotide primer and synthesizing an extension product of the second primer, wherein the extension product of the second primer is complementary to the extension product of the first primer; producing a new double-stranded nucleic acid comprising at least a portion of the extension product of the first primer and at least a portion of the extension product of the second primer and a full double-stranded restriction enzyme recognition sequence corresponding to the sequence of the one strand of the restriction enzyme recognition sequence of step; cleaving the new double-stranded nucleic acid from step with a restriction enzyme; and forming two or more shorter double-stranded nucleic acids, at least two of which comprise at least a portion of a copy of the linear double-stranded nucleic acid of step, thereby amplifying the linear double-stranded nucleic acid; wherein steps to are performed in a reaction mixture under isothermal conditions, and wherein the reaction mixture comprises: (i) the single-stranded RNA; (ii) a reverse transcriptase; (iii) the first polynucleotide adaptor and the second polynucleotide adaptor; (iv) the first polynucleotide primer and the second polynucleotide primer; (v) a ligase; (vi) a polymerase; and (vii) the restriction enzyme. (i) the single-stranded RNA; (ii) a reverse transcriptase; (iii) the first polynucleotide adaptor and the second polynucleotide adaptor; (iv) the first polynucleotide primer and the second polynucleotide primer; (v) a ligase; (vi) a polymerase; and (vii) the restriction enzyme.