Poster: Seed biology

Abs # 707: Analysis of zeins in mature wild-type and transgenic maize kernels by Matrix-Assisted-Laser-Desorption Ionization Time-Of-Flight Mass Spectrometry (MALDI-TOF MS)

Presenter:	Huang, Shihshieh , shihshieh.huang@monsanto.com
Authors	Huang, Shihshieh  (A)   Adams, Whitney R (A)   Michael, Luethy H (A)
Affiliations:	(A): Mystic Research, Monsanto Company

A high-throughput method has been developed to allow rapid analysis of maize seed storage proteins by MALDI-TOF MS. The extraction solution containing an organic solvent, a reducing agent and a volatile base, has been optimized to enable extraction of all classes of zein proteins (αaundefined-, βbundefined-, γgundefined-, and δdundefined-). A near-saturating concentration of matrix, 2-(4-Hydroxyphenylazo)-benzoic acid (HABA), was necessary to obtain strong peaks for the most lipophilic zeins, the αaundefined-zeins. Zein proteins with small mass differences, difficult to separate by SDS-PAGE, were resolved through this analysis. Mass signals corresponding to the 10-kD δdundefined-, 15-kD βbundefined-, 16-kD γgundefined-, 27-kD γgundefined-, and several 19-kD and 22-kD αaundefined-zeins were detected. The zein identities were further confirmed by the association of the number of cysteine residues in each zein MS peak, as determined by iodoacetamide derivatization, with the number predicted from its coding sequence. The relative zein abundance in the zein MS peaks was also correlated with the relative zein EST abundance among endosperm EST libraries. This method was utilized to examine the zein composition of a number of corn inbred lines, opaque mutants as well as transgenic lines that displayed zein reduction.