Plant seeds are an important food source for humans and animals. It is well known that in common bean seeds there are many anti-nutritional factors such as proteinaceous inhibitors that can inhibit α-amylases from mammalians and insects but not plants, and phytohemagglutinin (PHA) which is toxic to animals and insects. These proteins can also be considered as natural protective mechanisms against animal or insect predation. Since common bean has apparently been able to evolve these mechanisms, in this review we explore the implications of these, particularly in light of our recent research findings summarized below.
PHA from red kidney bean is capable of significantly enhancing the activity of porcine pancreatic α-amylase (PPA), with the potential of greatly assisting the digestion of bean starch in the pigs. However, in the cotyledons which comprise the bulk of food for animals, the net result of the co-existence of the stimulator (PHA) and α-amylase inhibitor seems to be that the latter could mask the effect of the former. Intriguingly, the major form of PPA inhibitor has previously been shown to be the product of αA1gene which is thought to be closely related to a PHA gene with some of the PHA gene sequences (corresponding to just only several amino acid residues) got truncated at some point of evolution. It is a moot point that diagonally opposed biological properties might be related through some common ancestral gene resulting in a dramatic reversal and advantage to the bean seed.
Genetic engineering of plants is still a controversial topic in the society as unforeseen effects could arise depending on insertion site in the genome of the host plant. An examination of the evolution of the α-amylase inhibitor gene in common bean can provide insights relevant to the public debate about genetic engineering of plants.
|Keywords:||Amylase Inhibitor, Plant Breeding, Evolution, Genetic Engineering of Plants, Genetic Modifications, Public Concerns|
Senior Lecturer, School of Biological Sciences, University of Canterbury, Christchurch, New Zealand
Ph.D. Student, University of Canterbury, New Zealand