Abstract:

【Objective】 To explore the molecular mechanism of graft healing in pecan, we cloned the CiMYB46 gene and analyzed its expression pattern and cis-elements. 【Method】 We extracted RNA from graft unions of pecan plants at different developmental stages and designed primers, based on our previous transcriptome results, to clone the desired gene by RT-PCR. In addition, genomic DNA was used as a template for PCR amplification and cloning of the promoter area of the desired gene.【Result】 The amplified fragment obtained by RT-PCR was cloned and sequenced. It contained an open reading frame of 969 bp that started with the initiation codon, ATG and ended with the termination codon, TAA, encoding a polypeptide of 322 amino acids. The deduced amino acid sequence of the cloned gene contained a MYB domain and was closely clustered withArabidopsis AtMYB46. Thus, we designated our sequence as CiMYB46. Real-time PCR analyses demonstrated that CiMYB46 was highly expressed during the vascular formation stage of graft union development in pecan and had a similar expression profile to that of some functional genes involved in secondary cell wall synthesis. A 1 070 bp promoter region upstream of the initiation codon of CiMYB46 was obtained through PCR and cloning, using genomic DNA as a template. PlantCARE analysis revealed that the promoter region of CiMYB46 contained two basic cis-acting elements, a CAAT box and a TATA-box, drought responsive elements, and hormone responsive elements, including ABA, Me-JA, GA, and SA. 【Conclusion】 CiMYB46 might be associated with vascular bundle formation during the graft healing process of pecan. It may be induced by GA.

Key words: Carya illinoinensis, grafting, gene cloning, CiMYB46, MYB transcription factor