Two distinct populations of neoblasts exist:

1. Sigma neoblast population 

2. Zeta neoblast population 

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MYB-related protein, now known as circadian clock associated 1 (CCA1), also plays a role in the circadian regulation of LHCB gene expression.

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Second but distinct MYB-related protein, late elongated hypocotyl (LHY), has also been identified as a potential clock gene.

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When the CCA1 gene is mutated so that no functional protein is produced, circadian and phytochrome regulation of four genes, including LHCB, is affected.

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A protein kinase (CK2)CKB3 can interact with and phosphorylate CCA1, which is a multisubunit protein with serine/threonine kinase activity.

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Phytochrome interacting factors (PIFs) act as negative regulators of photomorphogenesis.

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PIFs promote etiolated development in the dark (skotomorphogenesis) primarily by serving as transcriptional activators of dark induced genes.