Characterization of two members of the maize gene family, Incw3 and Incw4,encoding cell-wall invertases

Two maize putative cell-wall invertase genes (Incw3 and Incw4) have been is olated by screening a genomic DNA library (Zea mays L. W22) using the cDNA probes encoding the tu maize cell-wall invertases Incw1 and Incw2. The Incw 3 and Incw4 genes contain six exons/five introns and five exons/four intron s, respectively, The protein sequences deduced from both genes revealed a b eta-fructosidase motif and a cysteine catalytic site known to be conserved in invertase genes. A detailed analysis of the protein and nucleotide seque nces provides evidence that the Incw3 and the Incw4 genes encode putative c ell-wall invertases. Furthermore, the isoelectric point deduced from the IN CW4 protein sequence suggested that the Incw4 gene may encode a unique type of cell-wall invertase unbound in the apoplast. Gene expression studies us ing RT-PCR and in-situ RT-PCR hybridization showed that the Incw3 expressio n is organ/tissue-specific and developmentally regulated. In contrast, the Incw4 gene is constitutively expressed in all vegetative and reproductive t issues tested. (C) 2000 Elsevier Science B.V. All rights reserved.