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Abstract

Up to 80% of Zea mays L. grain phosphorus is stored in the form of phytin in the embryo. Our objective is to determine the control of phytin mobilization during germination and seedling growth. A maize phytase cDNA, phy S11, has been previously characterized (Maugenest et al., Biochem J 322: 511-517, 1997). In the present work, phy S11 was used to screen a maize genomic library and two distinct genes, PHYT I and PHYT II, were isolated and sequenced. The transcribed sequences of these two genes presented a strong homology whereas the untranscribed upstream and downstream sequences appeared very different. Northern blot analysis and in situ hybridization showed a high accumulation of phytase mRNA at the early steps of germination in the coleorhiza, radicle cortex and coleoptile parenchyma. Phytase expression was also detected at a lower extent in the scutellum. In adult plants, northern blot analyses revealed low but significant levels of phytase mRNA in the roots. In situ hybridizations on root cross-sections localized phytase mRNA in rhizodermis, endodermis and pericycle layers. Immunolocalization analysis showed phytase accumulation at the same sites as its mRNA. A RT-PCR approach was used in an attempt to discriminate between the transcripts from each gene in the different situations. These experiments indicate that both genes are expressed during germination, whereas only PHYT I is expressed in adult roots. This suggests that signals responsible for phytase gene expression in roots are different from those responsible for gene expression during germination.

Purification and Characterization of Three Phytases from Germinated Lupine Seeds (Lupinus albusVar. Amiga)

“…It was shown that phytases exist in multiple chromatographic forms in germinated lupine seeds. Multiple forms of phytases have already been identified in other plant species, such as barley (), wheat ( 23 , 36 , 37 ), spelt (), maize ( , ), rice (), soybean (), rapeseed (), pumpkin (), and lily ().…”

Globoids and Phytase: The Mineral Storage and Release System in Seeds

“…Screening a maize phage display library with this antibody yielded the first plant phytase nucleotide sequence ( PHYT I ): a HAP [ 68 ]. The subsequent screening of a maize genomic library using the cDNA clone as a probe provided two highly homologous genes ( PHYT I and PHYT II ) [ 69 ]. The two genes were shown to have an overlapping expression pattern, with PHYT I having the highest expression level.…”

“…A lower, but consistent, signal remained detectable in the roots after one month. The immunolocalization of the proteins revealed a similar pattern [ 69 ]. PHYT-I was expressed in E. coli .…”