Characterization of MSP1 Promoter and Identification of Transcription Factors Involved in Regulation of Abscisic Acid- and Ethylene-Responsive Gene Expression in Oil Palm

The 1,053-bp promoter of the oil palm metallothionein gene (so-called MSP1) and its 5´ deletions were analyzed in transiently transformed oil palm tissues. The full length promoter showed 7-fold higher activity in the mesocarp than in leaves and 1.5-fold more activity than the CaMV35S promoter in the mesocarp. Two positive regulatory regions at nucleotides (nt) -953 to -619 and -420 to -256 regions and a negative regulatory region at -619 to -420 nt region were identified within the promoter sequence. Fine-tune deletion analysis of the -619 to -420 nt region led to the identification of a novel negative regulatory AGTTAGG core-sequence, responsible for controlling the fruit-specific activity of the MSP1promoter. Abscisic acid (ABA) and copper (Cu2+) induced the activity of the promoter and its 5´ deletions more effectively than methyl jasmonate (MJ) and ethylene. Regulatory DNA motifs responsive to ABA, copper, MJ, and ethylene were identified within the promoter sequence. These results suggest that the MSP1 promoter and its regulatory regions are potentially useful for engineering fruit-specific and inducible gene expression in oil palm. ABF family of transcription factors (TFs) play important regulatory roles in plant response to abiotic stresses as well as plant growth and development. Two ABA-responsive cDNA clones, named EABF and EABF1 were isolated from oil palm fruits using yeast one-hybrid system. EABF had a conserved AP2/EREBP DNA-binding domain (DNA-BD) and a potential nuclear localization sequence (NLS). No previously known DNA-BD was identified from the EABF1 sequence. EABF and EABF1 proteins were classified as DREB/CBF and bZIP family members based on the multiple sequence alignment and phylogenetic analysis. Both proteins showed ABRE-binding and transcriptional activation properties in yeast. Furthermore, both proteins were able to trans-activate the down-stream expression of the LacZ reporter gene in yeast. EABF was induced in response to ABA in oil p