Date Palm - Genomics of Cultivated Palms - page 53

A draft nuclear genome for a Khalas variety female date palm [21] was assembled of
~380 Mb size, covering 60% of the genome and 90% of the genes. By sequencing eight
other cultivars, millions of SNPs were identified; some of them are also useful in discrim-
inating cultivars and to identify sex [21] . Draft date palm was mined for simple sequence
repeats and was revealed to contain  32,000 SSRs [42] . Genomic regions containing
Class I SSRs (repeat size  20) were annotated, of which many were either only hypo-
thetical proteins or transcription factors, protein kinases zinc finger proteins [42] , and so
on. The draft nuclear and plastid genome of date palm is a milestone in palm genomics
and the first of its kind in the Arecales. It also offers scope for further research on com-
parative genomics and computational genomics of other cultivated palms.
4.8 Proteomics
Proteomics is the study of the sum total of proteins of an organism. Three reports are
available on proteomes of date palm, providing insights to its genetic organization
[43-45] . Plant defense or stress-associated proteins were induced, while the energy
metabolism or photosynthesis-associated proteins were affected during the coloni-
zation of endophytic entomopathogenic fungi in date palms grown in field [43] . A
myosin heavy chain-like protein was accumulated in date palm grown in vitro when
inoculated with the same fungi [43] . About 21 proteins were identified during devel-
opment and germination of zygotic date embryos [44] . Enzymes of glycolysis, car-
bohydrate synthesis, protein translation, storage proteins, and stress-related proteins
were found during development and germination of zygotic date embryos. Storage
proteins such as glutelin, similar to that of oil palm, aldol reductase, and glyoxy-
lase I, were some of the important proteins identified during the study [44] . Eight
of the 23 identified proteins during somatic and zygotic embryogenesis were part of
the glycolysis pathway. Others were of carbohydrate biosynthesis, citrate cycle, ATP
synthesis, and amino acid metabolism. Most of the somatic embryo-specific proteins
identified belonged to glycolysis pathways, whereas those of the zygotic embryo
belonged to storage and stress-related proteins. Four are from stress-related and three
are from storage proteins, and three were not assigned any function [45] .
An understanding of such basic processes of proteomics sheds light on the
importance of storage or stress proteins or those involved in biochemical pathways.
However, investigation is needed in important processes such as the differences
between poor- and good-quality fruit, tissues infected by Bayoud pathogen in resist-
ant and susceptible cultivars, tissues affected by brittle leaf disorder, and in other
areas. Research about the proteins involved in such processes is essential to enhance
the knowledge and develop appropriate markers or kits for application in date palm
improvement.
4.9 Road Map for Date Palm Genomics
Date palm, Phoenix dactylifera L., is a perennial dioecious in North Africa and the
Middle East. It is also useful as a component of arid ecosystems and oases, and is