EAGER: Raphide Proteins and Taro Acridity

University Of Hawaii, Honolulu

Investigators

Abstract

Numerous crops cause skin edema and vesicle formation when handled or cause swelling of lips, mouth and throat, itchiness and pain when eaten without cooking. This irritation is referred to as acridity. Acridity has been reported in Kiwi fruit, a number of palms and ornamental plants (such as Dieffenbachia, daffodils, hyacinths and other bulb plants) and pose health risks to harvesters, children and pets. All the edible Aroids, including taro or dasheen, are acrid to varying degrees. Aroids such as taro's nutritious corm are eaten as a staple and the leaves as a vegetable by more than half a billion people. The cause of acridity is unknown. The current assay for acridity is to eat a small sample or rub a raw corm on the forearm of a test subject. More often than not, the test leads to the rapid withdrawal of test subjects from the study. The goals of this project are to determine the cause of acridity in taro so that potentially rapid breeding selection tool(s) can be developed to test for acridity. A viable solution to the acidity bottleneck would contribute to better food availability and new value-added products. This project is at the exploratory stage and could transform the molecular understanding of acridity, an anti-nutritional property of taro and other aroids. The common belief is that acridity is caused by sharp barbed needle-like calcium oxalate crystals (raphides). However, the fact that purified acrid raphides can be inactivated by proteinase with no change in raphide morphology suggests that proteins on the raphides cause acridity in an allergy type reaction. At least twenty-eight proteins are found on purified raphides. The goal of this project is to identify and validate which of these raphide-associated proteins are responsible for acridity in taro. Once identified, the protein(s) will be sequenced and predicted allergy-causing sequences will be further identified by sequencing. The sequences will then be used to develop a molecular assay for validating and associating the presence of the proteins with differences in acridity between taro varieties from Africa, Asian and Oceania. This project will be the first in-depth study to solving this major breeding bottleneck to improve the quality of taro, a traditional but neglected crop, and increase crop diversity and thereby increase the market opportunities' for small-farmers and rural households. Acridity data will be integrated into the European Union's Innovation & Networks Executive Agency (INEA) funded project on taro. Advanced training in biotechnology will be given and technology shared and coordinated with existing projects.