This Dinner Meeting will be enriched by our guest speaker Dr. Peggy Lemaux, the current President of ASPB (see her talk abstract below).
Registration information for this event will be available soon.
From Basic to Applied Research: How Modifying Thioredoxin Expression in Cereals Led to Unexpected Improvements in Grain Properties – So Where Are the Improved Crops?
Peggy G. Lemaux, Bob B. Buchanan, Department of Plant and Microbial Biology, University of California, Berkeley CA 94720
Thioredoxins (Trxs), ubiquitous low molecular weight proteins functional in cellular redox regulation, appear to be particularly important in plants, compared to other organisms. Work with barley, wheat, sorghum and a legume (Medicago truncatula) has established Trx h as a central regulatory protein in seeds through its action in reducing disulfide (S-S) groups of diverse seed proteins, such as storage proteins, enzymes and enzyme inhibitors. Compared to mammals, plants contain a large number of Trx genes. For example, 19 different genes for classical Trxs have been identified in Arabidopsis thaliana; Trx gene families have also been identified in cereals, like rice, barley, wheat and sorghum. Extensive evidence indicates that adding Trx, NADPH, and NADP-thioredoxin reductase (NTR) to flour or seed preparations from a number of cereals results in changes in the redox state of their storage proteins due to reduction of S-S linkages. These early in vitro protein studies were complemented with experiments based on genetic engineering of cereal grains. Barley seeds, with Trx h overexpressed in the endosperm and targeted to the protein body, showed accelerated germination and early or enhanced expression of associated enzymes, i.e., α-amylase and pullulanase. Additional manipulations of the levels of Trx h in wheat grain were subsequently shown to (i) enhance protein solubility and digestibility, (ii) reduce allergenicity of wheat gliadins, (iii) improve dough quality from poor quality wheat flour and, most recently, (iv) reduce the incidence of preharvest sprouting in experiments that were validated in the field. Similar work in sorghum has revealed accelerated germination and, preliminarily, increased digestibility of seed proteins. These observations led to the intriguing question of how such changes in the endosperm are communicated within, and possibly outside, the seed. Observations on a single thioredoxin, trx h9, revealed that it is a membrane-associated protein, capable of moving from cell-to-cell, providing suggestive evidence for a role of this Trx h in intercellular communication. Some of the improvements realized through the manipulation of thioredoxin could be important in the commercial marketplace but none have made it there – in part due to implications from the other important aspect of my faculty position – namely consumer and end user reactions to genetically engineered crops and foods.