Os05g0405000

The rice gene Os05g0405000 was reported as flo4 in 2005 by researchers from Korea and Japan.

Annotated Information

Gene Symbol

• Os05g0405000 <=> flo4, flo4-2, flo4-3, ppdk, OsPPDK, PPDK1, CPDK1, PPDKB, OsPPDKB, cyOsPPDKB, OsPBDK, PBDK, osppdkb

Function

• OsPPDKB gene encodes pyruvate orthophosphate dikinase (PPDK).
• Cytosolic PPDK functions in rice to modulate carbon metabolism during grain filling.

Mutation

Figure 1. Phenotypes of flo4 kernels. .

• The researchers conducted a screening for GUS activity to identify knockout mutations in the genes expressed in mature seeds. Among the several hundred GUS-positive lines that were identified, we found one in which the white-core endosperm mutant phenotype co-segregated. This floury mutation was recessively segregated (Figure 1a), and was named floury-4 (flo4).

• Cross-sectioning revealed that the interior of the endosperm was floury-white while the outer portion was normal (Figure 1d). This suggests that starch accumulation was abnormal in the early stages of ripening, but recovered later on in development. The scanning electron microscopic analysis showed that the white endosperm comprised round and loosely packed, compound starch granules (Figure 1f).

Expression

Figure 3. Expression analysis by RT-PCR and GUS assay. .

• Expression analyses demonstrated that the cytosolic mRNA of OsPPDKB was induced in the reproductive organs after pollination, and greatly increased until about 10 days after fertilization.
• This mRNA was localized mainly in the endosperm, aleurone, and scutellum of the developing kernel.

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Labs working on this gene

• Laboratory of Plant Functional Genomics, Division of Molecular and Life Sciences, Pohang University of Science and Technology, Pohang 790-784, Korea, and
• Bioscience Center, Nagoya University, Aichi 464-01, Japan