Os03g0737701

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Annotated Information

Function

• MIK could determine the fate of myo-inositol especially in seed.
• OsMIK is necessary for wild type levels of seed phytic acid, but not essential for viability.

Mutation

• In order to conWrm that these two mutants are lpa mutants, the seed total P, phytic acid-P (PA-P) and inorganic P (Pi) contents were examined (Table 1).

Table 1 Comparison of seed myo-inositol, phytic acid and inorganic P contents of lpa mutants and wild-types. .

• Seed extracts of lpa mutants were subjected to HPLC analysis to determine if the other inositol phosphates were aVected by the mutation. Comparison to wild-type Nipponbare and inositol phosphate standards revealed that N15- 186 seeds are signiWcantly reduced in PA and inositol monophosphate while exhibiting an increase in Pi (Fig. 1). No signiWcant accumulation of other inositol phosphate intermediates (InsP2 to InsP5) was detected under the conditions used. The HPLC elution proWle of N15-375 showed an increase in Pi and a decrease in PA, but no other signiWcant changes were observed (Fig. 1).

Fig. 1 HPLC chromatograms of inositol phosphates. a Inositol phosphate standards, retention times for the various inositol phosphates were: Ins(2)P1, 9.5 min; Pi, 15.5 min, Ins(1,4)P2, 21 min; Ins(1,3,4)P3, 32 min; Ins(13,4,5)P4, 33 min; Ins(1,3,4,5,6)P5, 35 min; and Ins(1,2,3,4,5,6)P6, 29 min. b Nipponbare wild-type, c N15-186 lpa mutant, d N15-375 lpa mutant .

• The GC–MS analysis revealed that the myo-inositol content, as well as those of other sugars (glucose, fructose and galactose), was increased in the N15-186 mutant compared to the wild-type (Fig. 2). The myo-inositol content of N15-186 seed was ninefold greater than wild-type, while the other sugars examined were 2–3 fold higher. In contrast, the myo-inositol content of N15-375 mutant seeds did not diVer from wild-type.

Fig. 2 GC–MS analysis of myoinositol and other carbohydrates as alditol hexaacetate derivatives from seed extracts of wild-type, N-186 and N-375 mutants. .

Expression

• RT-PCR analysis of total RNA from various tissues including shoot, root, and panicle indicated that OsMIK is expressed in all tissues (Fig. 6). Higher expression was detected in the vegetative shoot tissue compared to the reproductive tissue with relatively lower expression in the roots. A search of publicly available rice EST data indicated that OsMIK is expressed in callus, leaf, root, shoot and panicle tissues (http://www.tigr.org/).

Fig. 6 Expression analysis of OsMIK in diVerent tissues of wild-type plant. RT-PCR analysis was performed using total RNA from various tissues [shoot (B) = leaf blade, shoot (s) = leaf sheath/stem, root and panicle] of wild-type Nipponbare and primers for OsMIK and actin (control) .

Evolution

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Labs working on this gene

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