Analysis of the <i>Euglena gracilis</i> chloroplast genome

Keller, Mario; Rutti, B.; Stutz, Erhard

doi:10.1016/0014-5793(82)81088-0

Cited by 10 publications

(1 citation statement)

References 24 publications

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“…Precursor mRNAs and excised intron sequences of the psbA gene were detected on Northern blots. The structure of these precursors was not analysed, and it was not clear whether the introns from a pre-mRNA are removed in a strict order, or randomly, as was suggested (Keller et al, 1982;Hollingsworth et al, 1984).…”

Section: Introductionmentioning

confidence: 99%

The structure of precursor mRNAs and of excised intron RNAs in chloroplasts of Euglena gracilis

1985

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Partially spliced precursor mRNAs (pre‐mRNAs) in the steady‐state population of RNA from chloroplasts of Euglena gracilis were found by electron microscopy. The structure and the frequency of the pre‐mRNAs of the psbA gene (the gene for the 32‐kd protein of photosystem II), which is split by four introns in Euglena chloroplasts was analysed by electron microscopy. A chloroplast DNA (cpDNA) fragment containing the psbA gene from Euglena, was cloned into a pEMBL vector. The single‐stranded recombinant phage DNA of the coding strand was prepared and hybridized with cpRNA. The majority of hybrids were formed with mature mRNA, but ˜8% of the hybrids were formed with pre‐mRNAs. The pre‐mRNAs were either unspliced or incompletely spliced. A detailed analysis of the structure and the frequency of the pre‐mRNAs of the psbA gene showed that the four introns are neither spliced out in a strictly random way, nor in a 5′‐3′ or 3′‐5′ direction. Introns 2 and 3 are preferentially spliced out first, intron 1 intermediately and intron 4 is generally spliced out last. However, this sequence is not a strict rule. We conclude that the introns can be spliced independently, each one at a different rate. The coding strand from a fragment of the psbA gene was separated and annealed with low mol. wt. cpRNA, which was isolated from an agarose gel. Small circular hybrids were found at the positions of the four introns, demonstrating for the first time covalently closed circular excised intron RNAs (iRNAs) in chloroplasts.

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Section: Introductionmentioning

confidence: 99%

The structure of precursor mRNAs and of excised intron RNAs in chloroplasts of Euglena gracilis

1985

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Light regulation of the cell cycle in Euglena gracilis bacillaris

Yee

Bartholomew

1988

Cytometry

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We have studied the light regulation of the cell division cycle in the photosynthetic alga Euglena gracilis bacillaris. Euglena grown under phototrophic conditions are easily synchronized to a 12 h light‐12 h dark regime. By inoculating stationary phase, nondividing cells into fresh media and exposing the diluted cells to either light or darkness, we have determined that initiation of DNA synthesis for the cell division cycle is light dependent. By varying the length of time in light to which synchronized cells are exposed, we have shown that commitment to the cell cycle requires exposure to more than 6 h of light. We propose that this is to allow the accumulation, through photosynthetic electron transport, of an initiating factor that will enable DNA synthesis to begin. Flow cytometry analysis also shows that once cells are committed to the cell cycle, they complete the cycle in the dark, so mitosis is a light‐independent step.

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