THE MAIZE GAMMA-ZEIN SEQUESTERS ALPHA-ZEIN AND STABILIZES ITS ACCUMULATION IN PROTEIN BODIES OF TRANSGENIC TOBACCO ENDOSPERM

Zeins are seed storage proteins that form accretions called protein bo dies in the rough endoplasmic reticulum of maize endosperm cells, Four types of zeins, alpha, beta, gamma, and delta, aggregate in a distinc tive spatial pattern within the protein body, We created transgenic to bacco plants expressing alpha-zein, gamma-zein, or both to examine the interactions between these proteins leading to the formation of prote in bodies in the endosperm, Whereas gamma-zein accumulated in seeds of these plants, stable accumulation of alpha-zein required simultaneous synthesis of gamma-zein, The zein proteins formed accretions in the e ndoplasmic reticulum similar to those in maize endosperm, Protein bodi es were also found in protein storage vacuoles, The accumulation of bo th types of zeins peaked early in development and declined during matu ration, Even in the presence of gamma-zein, there was a tu mover of al pha-zein, suggesting that the interaction between the two proteins mig ht be transitory, We suggest that gamma-zein plays an important role i n protein body formation and demonstrate the utility of tobacco for st udying interactions between different zeins.