A zebrafish-specific chimeric gene evolved essential developmental functions: discussion of conceptual significance

The tobacco rbcS (ribulose bisphosphate carboxylase small subunit) promoter, fused to the β-glucuronidase (GUS) reporter gene, was delivered to black spruce (Piceamariana (Mill.) BSP) tissues via microprojectile DNA bombardment, and its regulation was studied. The expression of the tobacco rbcS promoter–GUS chimeric gene was dependent on the presence of chloroplasts in black spruce tissues, as demonstrated in two ways: (i) there was no GUS activity expressed in zygotic embryos where no chloroplasts were observed, whereas it was expressed in light- and dark-grown seedlings that contained mature or immature chloroplasts; (ii) a herbicide, Norflurazon, destroyed chloroplast structure in seedlings and inhibited the expression of the tobacco rbcS promoter–GUS chimeric gene. A control chimeric gene, the cauliflower mosaic virus (CaMV) 35S promoter–GUS fusion gene was not inhibited by Norflurazon. Unlike in angiosperms, light had no effect on the expression of tobacco rbcS promoter–GUS chimeric gene. Both light- and dark-grown seedlings showed GUS activity, and expression in dark-grown seedlings was not enhanced by light. These results suggest that the tissue-specific regulation of the rbcS promoter may be conserved between angiosperms and conifers, but that the light regulation of this promoter may not be conserved.

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Sequences controlling transcription of the Chlamydomonas reinhardtii beta 2-tubulin gene after deflagellation and during the cell cycle

Molecular and Cellular Biology ◽

10.1128/mcb.14.8.5165-5174.1994 ◽

1994 ◽

Vol 14 (8) ◽

pp. 5165-5174

Author(s):

J P Davies ◽

A R Grossman

Keyword(s):

Cell Cycle ◽

Chlamydomonas Reinhardtii ◽

Transcription Initiation ◽

Chimeric Gene ◽

Transcriptional Level ◽

Sequence Motif ◽

Tubulin Gene ◽

Rich Region ◽

Beta 2 ◽

Encoding Genes

In Chlamydomonas reinhardtii, transcripts from the beta 2-tubulin gene (tubB2), as well as those from other tubulin-encoding genes, accumulate immediately after flagellar excision as well as at a specific time in the cell cycle. Control of tubB2 transcript accumulation following deflagellation is regulated, at least partially, at the transcriptional level. We have fused the tubB2 promoter to the arylsulfatase (ars) reporter gene, introduced this construct into C. reinhardtii, and compared expression of the chimeric gene with that of the endogenous tubB2 gene. After flagellar excision, transcripts from the tubB2/ars chimeric gene accumulate with kinetics similar to those of transcripts from the endogenous tubB2 gene. The tubB2/ars transcripts also accumulate in a cell cycle-specific manner; however, chimeric transcripts are more abundant earlier in the cell cycle than the endogenous tubB2 transcripts. To elucidate transcriptional control of tubB2, we have mutated or removed sequences in the tubB2 promoter and examined the effect on transcription. The tubB2 promoter shares features with the promoters of other tubulin-encoding genes; these include a GC-rich region between the TATA box and the transcription initiation site and multiple copies of a 10-bp sequence motif that we call the tub box. The tubB2 gene contains seven tub box motifs. Changing the GC-rich region to an AT-rich region or removing three of the seven tub box motifs did not significantly affect transcription of the chimeric gene. However, removing four or five tub box motifs prevented increased transcription following deflagellation and diminished cell cycle-regulated transcription from the tubB2 promoter.

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