Oil Palm - Genomics of Cultivated Palms - page 30

Promoters are regions upstream of the coding sequences of the genes and play
a crucial role in tissue-specific and condition-specific expressions. A mesocarp
tissue-specific promoter of the mesocarp-specific metallothionein-like gene promoter
(also known as MSP1; accession no: EU499363) corresponding to the oil palm
MT3-A gene has been cloned and sequenced for use in the genetic engineering of
oil palm [26] . This promoter is tested using the uidA reporter gene in bacterial [27]
systems ( E. coli, Agrobacterium tumefaciens ). The promoter is metal inducible in
the presence of metals such as copper due to a copper-inducible motif GTAC in the
sequence. The 986 bp fragment also has TATA box and ethylene-responsive elements
[27] and fruit tissue-specific AGTTAGG motif [28] . The promoter is induced by the
presence of abscisic acid (ABA) and copper [28] . Further, secrets of oil biosynthesis
are reviewed and summarized [29] with special reference to oil palm.
3.3 Transcriptomics and Genes of Somatic Embryogenesis
and Mantled Disorder
Transcriptome analysis of callusing and somatic embryogenesis of oil palm identi-
fied a glutathione S-transferase as a highly expressed gene in nonembryogenic callus
[30,34] . Unigenes analysis of the transcriptome indicated 648 nonredundant sim-
ple sequence repeats and 211 putative full-length open reading frames [30] . Egpk1,
EgHOX1, EgPER1, and OPSC10 are the four highly expressed genes in embryo-
genic cultures of oil palm [31] . EgLSD (a putative lignostilbene-a,b-dioxygenase)
and EgER6 (a putative ethylene-responsive gene) were the auxin-responsive genes
in the suspension cultures of oil palm [32] . A putative serine-threonine kinase (DQ
267436) was also found expressed in tissue cultures of oil palm [33] . Recently, 928
annotated unigenes were identified in the transcripts during the somatic embryogen-
esis [34] . In this study, a transcript for a guanine nucleotide-exchange protein GEP2
was found only in the initiation library (GH635901-GH637767). The majority of
the defense-related transcripts in the library were coded as either methallothionein-
like or peroxidase-related proteins. Other ESTs with protein destination and storage
functions are related to the ubiquitin/26S proteosome pathway [34] . In the embryoid
cDNA library of oil palm, 325 unigenes (DW 247764-DW 248770) were identified
in different tissues: germinA in 15-week-old kernel, Myb1trancription factor in spear
leaves, and LEA (late embryogenesis abundant) genes in seedling roots [35] .
Multiplication of oil palm by tissue culture via somatic embryogenesis produces
3-5% of off-type plants with a homeotically modified flower structure known as
mantled . In these plants, fertile or sterile androecium is transformed into carpel-
like structures, thereby lowering oil yields in mantled palms. Mantled and normal
inflorescences were analyzed using molecular biology, and two genes associated
with the difference were discovered as EgFB1 and EgRING. These two genes are
down-regulated in the mantled inflorescences and known to encode for proteolytic
signaling proteins [36] . MET, CMT, and DRM are the methyl transferases (EU
117216-EU117218), and DNA methylation differences were noticed in mantled