Coconut - Genomics of Cultivated Palms - page 21

and features are listed in Table 2.3 . KNOX genes of coconut resembled that of oil
palm, whereas CDKA genes of coconut resembled the tree Picea or rice or maize.
SERK genes of coconut resembled rice benzothiadiazole-induced SERK genes. The
role of benzothiadiazole in enhancing tissue culture is inferred from the study. We
attempted a similar search of coconut SERK genes using NCBI BLAST, but we
could not get any match with known SERK genes for the first 70-80 base pairs of
the sequence. However, this region matched with either a hypothetical protein or a
whole genome shotgun sequence, which is worth exploring.
2.6 Structural Biology of Hirsutellin
Eriophyid mite, an important pest of coconut in LAC countries, later spread to many
Asian and African countries. The pest has become a serious threat to coconut cultiva-
tion except in the Pacific region. Chemical control methods are neither eco-friendly
nor easy to practice. Biological control and resistance breeding are the only options
left. Markers for resistance are identified [37] and need to be converted to reliable
SCAR markers and kits after validation on a large number of samples. The bio-
logical control agent of fungal pathogen Hirsutella thompsonii [56] offers promise.
Hirsutellin A (HtA) is an extracellular protein produced by the invertebrate, resem-
bling a ribotoxin similar to sarcin. The structural biology of the protein [59-61]
reveals many interesting observations. Initially, HtA toxin was identified and was not
proved to have a role in pathogenicity [57] . Later studies confirmed the toxicity and
led to identification of the complete gene sequence [58] and corresponding protein
[59] . NMR studies indicated a characteristic feature of a alpha  beta fold with a high
positive charge at surface [60] . Asp40 in the smallest ribotoxin (HtA) is crucial in
providing electrostatic interactions and biological activity [61] . Details of the studies
on the toxin and its structural biology are given in Table 2.4 .
2.7 Road Map for Coconut Genomics
A database resource was developed for all coconut researchers, covering genom-
ics, pathology, microbiology, and genetics [62] . Another database of coconut [63]
is a useful resource with markers and map position data for the coconut genomic
research community. Microsatellites developed for coconut are also useful in rat-
tans [64] , oil palm [65] , and other palms [66] . WRKY sequences recently obtained
from coconut [66] and protein kinase sequences [67] are important resources for
development of gene-specific markers in palms for tagging disease resistance and
phylogenetics studies. Coconut genomics is still in the take-off stage and can reach
similar heights to those of oil and date palm by harnessing comparative genomics.
Molecular marker resources and kit are available for the characterization of coconut
germplasm. The knowledge available on marker-trait association and/or QTLs for
seedling traits, yield, fruit component traits, epicuticular wax components, and resist-