Divergent Gene Amplification Based on Whole-Genome Sequences

Friday, 14 February 2014
Crystal Ballroom A (Hyatt Regency Chicago)
Joachim Messing , Rutgers University , Piscataway, NJ
The seeds of maize and other cereal grasses are the main source of calories on
earth, mainly due to their high carbohydrate content (reaching about 80%). Not
surprisingly, such a concentration of starch has resulted in industrial applications,
even if energy output characteristics do not rival conventional fuels. Such
applications threaten to strangle food supplies in places where there are no
alternatives. At the same time it is important to recognize that cereal seeds have
critical shortcomings even in their traditional uses as food and feed: Humans and
livestock cannot synthesize all the amino acids they need from those calories
and therefore need to supplement those in their diet. Lack of essential amino
acids in the diet can lead to severe, even life-threatening conditions.
Food or feed does not provide these essential amino acids in free form, but in the
form of proteins that upon digestion are released into the blood stream.
Therefore, the composition of seed proteins presents a critical bottleneck in the
world's food supply. Fortuitously, this is precisely where genomics offers critical
insights with practical potential. In cereals, the seed proteins – whose amino acid
composition determines the nutritional quality of food and feed – are dominated
by small gene families that are highly expressed. The genes encoding them have
evolved through gene amplification in tandem and by dispersal throughout the
genome. Comparative analysis of whole-genome sequences of a number of
species of the grass gene family can now be used to re-trace gene copies and
their divergence in structure during speciation. Their divergence explains, for
example, why seed proteins of some cereals are more suitable for making bread
and noodles than others but also can trigger autoimmune diseases in certain
human haplotypes. On the other hand, divergence of these gene copies has not resulted in proteins
with essential amino acid compositions that are needed for a balanced diet. Here,
however, our knowledge of gene sequences and expression profiles permits us
to use novel genetic approaches to re-balance the expression of genes during
seed development and achieve levels of proteins with essential amino acids that
can meet the dietary needs of humans and livestock.