ZRP2 - A NOVEL MAIZE GENE WHOSE MESSENGER-RNA ACCUMULATES IN THE ROOTCORTEX AND MATURE STEMS

A near full-length cDNA clone (pZRP2) was isolated from a cDNA library constructed from maize root mRNAs. The predicted polypeptide has a ca lculated molecular mass of 66 975 Da, is largely hydrophilic, and cont ains 26 repeats of a motif the consensus sequence of which is RKATTSYG [S][D/E][D/E][D/E][D/E][P]. The function of the putative protein remai ns to be elucidated. The ZRP2 mRNA accumulates to the highest levels i n young roots, and is also present in mature roots and stems of maize. Further analysis of young roots indicates that the lowest level of ZR P2 mRNA is near the root tip, with relatively high levels throughout t he remainder of the root. In situ hybridization reveals that ZRP2 mRNA accumulates predominantely in the cortical parenchyma cells of the ro ot. In vitro nuclear run-on transcription experiments indicate a drama tically higher level of zrp2 gene transcription in 3-day old roots tha n in 5-day old leaves. A zrp2 genomic clone, which includes the transc ribed region and 4.7 kb of upstream sequence, was isolated and charact erized.