Abstract: [Objective] Stress is one of the main factors affecting growth, development and formation of biological production and quality of plant. As non-coding genes, miRNAs play important roles in regulating plant growth and the processes of stress resistance. To reveal the function of miR397 and miR1432 in bamboo and provide a basis for molecular design of bamboo resilience breeding in future, the structural features of miR397 and miR1432 precursor sequences from Phyllostachys edulis were analyzed, the tissue-specific expression analysis as well as the expression changes of miR397 and miR1432 under abiotic stresses of drought, temperature, light, NaCl and hormone treatment were carried out.[Method] The precursor sequences of miR397 and miR1432 of P. edulis were isolated using stem-loop primer method and RT-PCR technology, online platform Web LOGO was used for the conservation analysis of mature miRNA. MEGA 6.0 software was used for the construction of phylogenetic tree with miRNA precursor sequences. The secondary structure of the two precursors was predicted with the online platform RNAfold WebServer. The sequences of 1500 bp upstream of the precursor of phe-miR397 and phe-miR1432 were direct-downloaded respectively from BambooGDB and acting elements analysis was performed using online platform Plant CARE. Real-time quantitative PCR method was used for the tissue-specific expression analysis of phe-miR397 and phe-miR1432 in bamboo roots, stems, leaves and sheaths, and the expression changes in bamboo leaf after 2 h treatments of darkness, high light intensity (1 500 μmol·m^-2s^-1), high temperature (42 ℃), low temperature (4 ℃), NaCl (250 mmol·L^-1), GA₃ solution (100 μmol·L^-1) and ABA solution (100 μmol·L^-1) respectively.[Result] The isolated precursor sequences of phe-miR397 and phe-miR1432 were all 88 bp, containing 21 bp mature sequences correspondingly. The precursors of phe-miR397 and phe-miR1432 could fold into stable stem-loop structure, and the mature sequences were generated at 5' end of the arm in the stem-loop structure respectively. Overall, the nucleotide conservative in mature sequence of miR1432 family was higher than that of miR397 family. Both are containing the essential elements of promoter, such as TATA-box and CAAT-box, in the regulatory region of the upstream precursors of phe-miR397 and phe-miR1432. At the same time, many stress (light, drought, temperature, etc.) related response elements and hormone-responsive elements were found, indicating phe-miR397 and phe-miR1432 may be regulated by stress and hormone. Both phe-miR397 and phe-miR1432 expressed in leaf sheath with the highest level, while the lowest in young stem for phe-miR397 and in leaf for phe-miR1432. The expression of phe-miR397 and phe-miR1432 in leaf were all down-regulated after 2 h with the treatments of high light intensity , darkness, 42 ℃, 4 ℃ and NaCl. The expression of phe-miR397 was down-regulated under drought treatment as well as ABA, while that of phe-miR1432 was up-regulated. The expression of phe-miR397 was up-regulated and phe-miR1432 was down-regulated for GA₃ treatment.[Conclusion] As two conservative miRNAs in bamboo, the expression of phe-miR397 and phe-miR1432 were either up- or down-regulated under the stress treatments of light, temperature, drought and NaCl, as well as ABA and GA₃ treatments, indicating that they might play important regulatory roles in respond to abiotic stress resilience in bamboo, which were also associated with the regulation of endogenous hormones.

Key words: Phyllostachys edulis, miRNA, abiotic stress, hormones