The oil palm metallothionein promoter contains a novel AGTTAGG motif conferring its fruit-specific expression and is inducible by abiotic factors

Abstract

The 1,053-bp promoter of the oil palm metallothionein gene (so-called MSP1) and its 5' deletions were fused to the GUS reporter gene, and analysed in transiently transformed oil palm tissues. The full length promoter showed sevenfold higher activity in the mesocarp than in leaves and 1.5-fold more activity than the CaMV35S promoter in the mesocarp. The 1,053-bp region containing the 5' untranslated region (UTR) gave the highest activity in the mesocarp, while the 148-bp region was required for minimal promoter activity. Two positive regulatory regions were identified at nucleotides (nt) -953 to -619 and -420 to -256 regions. Fine-tune deletion of the -619 to -420 nt region led to the identification of a 21-bp negative regulatory sequence in the -598 to -577 nt region, which is involved in mesocarp-specific expression. Gel mobility shift assay revealed a strong interaction of the leaf nuclear extract with the 21-bp region. An AGTTAGG core-sequence within this region was identified as a novel negative regulatory element controlling fruit-specificity of the MSP1 promoter. Abscisic acid (ABA) and copper (Cu(2+)) induced the activity of the promoter and its 5' deletions more effectively than methyl jasmonate (MeJa) and ethylene. In the mesocarp, the full length promoter showed stronger inducibility in response to ABA and Cu(2+) than its 5' deletions, while in leaves, the -420 nt fragment was the most inducible by ABA and Cu(2+). 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.

Plant Metallothioneins: Putative Functions Identified by Promoter Analysis in Silico

“…The G-box element was already identified in the promoter of the gene encoding type 2 metallothionein in L. esculentum (Whitelaw et al, 1997). The G-box motif was also found in the promoters of the oil palm genes MT3-A and MT3-B (Omidvar et al, 2010 Cis elements governing cell-and organ-specific expression are also present in the MT promoters…”

“…4). Previously it has been found in MT gene promoters in T. aestivum (Giritch et al, 1998), Hordeum vulgare (Ozturk et al, 2002, P. juliflora (Usha et al, 2009), E. guineensis (Omidvar et al, 2010) andP. coarctata (Usha et al, 2011).…”

“…In silico analysis of the 1.15 kb promoter region of the Casuarina glauca MT1 gene revealed the presence of three 5'-TGACG-3' motifs (Oberlello et al, 2007). Omidvar et al (2010) showed the presence of the MeJa-responsive element in the E. guineensis MT promoter sequence.…”

“…4). The ERE motif has been found in the promoters of P. juliflora PjMT1 andPjMT2 (Usha et al, 2009), P. coarctata PcMT3 (Usha et al, 2011), E. guineensis metallothionein (Omidvar et al, 2010) and L. esculentum LeMTb (Whitelaw et al, 1997). Expression of the latter gene is higher in mature leaves than in young leaves (Giritch et al, 1998).…”

“…Few plant MT gene promoters have been described to date. Previously studied plant MTs include those from Lycopersicon esculentum (Whitelaw et al, 1997), Pisum sativum (FordhamSkelton et al, 1997), Pseudotsuga menziesii (Chatthai et al, 2004), Citrus unshiu (Endo et al, 2007), Phaseolus vulgaris (Qi et al, 2007), Elaeis guineensis (Omidvar et al, 2010) and O. sativa (Dong et al, 2010).…”