There are five phytochrome isoforms in angiosperms

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#Id: 4760

#Unit 5. Developmental Biology

Embryos lacking PAL-1 have no somatic cell types derived from the C and D stem cells.

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#Id: 4761

#Unit 5. Developmental Biology

PAL-1 is regulated by the MEX-3 protein, an RNA binding protein that inhibit the translation of pal-1 mRNA.

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#Id: 4762

#Unit 5. Developmental Biology

In mex-3-deficient mutants, PAL-1 is seen in every blastomere.

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#Id: 4763

#Unit 5. Developmental Biology

SKN-1 also inhibits PAL-1 (preventing it from becoming active in the EMS cell).

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#Id: 4764

#Unit 5. Developmental Biology

In the germ line, PAL-1 synthesis is prevented by the PUF-8 protein, which binds to the 3′ UTR of pal-1 mRNA and blocks its translation.

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#Id: 4765

#Unit 5. Developmental Biology

 PIE -1, is necessary for germline cell fate.