Abstract:

【Objective】 The aim of this research is to clone the full-length DNA sequences encoding NAC domain protein in pear, and to find out whether the long-distance movement of the NACP mRNA via the phloem. 【Method】 The full-length sequences encoding NAC domain protein were isolated from Pyrus bretschneideri Yali and Pyrus betulaefolia Bunge by the homology cloning method. Bioinformatics methods were used for sequence analysis. Heterograft experiments were performed by using Pyrus betulaefolia Bunge as the rootstock and Pyrus bretschneideri Yali as the scion. Samples were taken from the outer tissue of scion and rootstock, where the phloem cells lie, in addition to the shoot apex and leaf of the scion. The amplified products were digested by the specific restriction enzyme ScrFⅠ. To identify the precise location of NACP transcripts, in situ hybridization studies were conducted on the transverse sections of rootstock. Dl-NACP mRNA was detected in the phloem by antisense probe. 【Result】 The full-length of NACP consisted of 1 377 bp encoding 350 amino acids. They contained two introns whose size was 111 bp and 96 bp, respectively. Restriction enzyme digestion results showed that there were the stock NACP gene expressions in apex, leaf, stem phloem of the scion, while there was the scion NACP gene expression in the stock phloem, but not in the xylem. 【Conclusion】 All of the results indicate that the obtained genes are the new members of the NAC domain protein gene family. The concept that the endogenous RNA molecules circulate throughout the plant via the phloem proved to be correct. The results have laid a foundation for study of the mechanism of rootstock and scion interactions.

Key words: pear, NAC domain protein, mRNA, graft, molecular transport