“Chloroplast genes encoding subunits of the H +-ATPase complex of Chlamydomonas reinhardtii are rearranged compared to higher plants: sequence of the atpE gene and location of the atpF and atpI genes.”

The purpose of this study was to locate the three remaining genes (atpE, atpF, and atpI) that encode for the ATPase subunits on the Chlamydomonas reinhardtii chloroplast genome. Once located, they noticed that the three genes, in addition to the rest of the subunit encoding genes, were scattered around the genome. This result was uniquely different than what they have found with most non-algal plant life, where the corresponding genes were found within a few dozen bp of one another. In addition, even photosynthesizing cyanobacterial species exhibited some form of “ordered” placement in their ATPase encoding genes, which makes this algal species’ gene placement particularly unique.

Reference:

Woessner J.P, Gillham N.W., and Boyton J.E. 1987. Chloroplast genes encoding subunits of the H +-ATPase complex of Chlamydomonas reinhardtii are rearranged compared to higher plants: sequence of the atpE gene and location of the atpF and atpI genes. Plant Molecular Biology 8: 151-158.

(http://www.springerlink.com/content/k857175q760mh250/fulltext.pdf)

“Tissue-Dependent Plastid RNA Splicing in Maize: Transcripts from Four Plastid Genes Are Predominantly Unspliced in Leaf Meristems and Roots”

RNA splicing is generally considered an essential part of transcription, however, it may have been found that spliced genes do not so much dictate the level of gene activity but rather the origin of the tissue sample.

In this study, major players of the plastid genome (atpF, petB, petD, and rpl16)  both spliced and unspliced were accounted for in leaf, meristematic, and root tissue of a maize inbred B73.  The results were interesting.  As expected, spliced genes were commonly found in new formation of leaf tissue and meristematic and root tissue had a largely unspliced plastid genome in comparison.  However, while tissue origin showed a significant difference in spliced to unspliced genome ratios, there was not a significant difference between normal maize and those in mutants blocking photosynthetic electron transport.  Both seedlings grown in the dark and mutants blocking chlorophyll accumulation also yielded similar RNA ratios.  This shows that photosynthetic competency, chlorophyll content, and exposure to light do not have a direct effect on the ratio of spliced to unspliced plastid genome and that it seems to rely solely on the differentiation of plant tissue.

Reference:

Barkan, Alice. January 4, 1989. Tissue-Dependent Plastid RNA Splicing in Maize: Transcripts from Four Plastid Genes Are Predominantly Unspliced in Leaf Meristems and Roots. The Plant Cell, Vol 1., 437-445.
http://www.plantcell.org/content/1/4/437.full.pdf

 

*post edited 12/12/2011

Correct splicing of a group II intron from a chimeric reporter gene transcript in tobacco plastids

In this research, an in vivo test system is assembled in order to perform a study on group II intron splicing. Group II intron splicing is studied because it tends to interrupt reading frames in plastid and bacteria. The gene, udiA, is a chimeric reporter gene which is transcribed in tobacco plants. This gene is formed by fusing the tobacco plastid DNA region (which contains the atpF gene intron) with the region of the plastid that codes for the udiA chimeric reporter gene. The atpF intron is specifically chosen for this study because it is the smallest of the introns found in tobacco plastid DNA. Furthermore, a northern blot analysis is performed to confirm that the correct intron is removed. Upon viewing the results, it was discovered that the atpF gene region contained adequate amounts of nucleotides for both upstream and downstream exons to correctly splice a group II intron.  Through this research, it was concluded that the plasmid transformants were not affected by atpF splicing. This indicated that the atpF intron excision is not the reason for the ineffective splicing ability of group II intron by the chimeric reporter gene udiA in tobacco plastids.

Reference:

Bock, Ralph, and Pal Maliga. 1995. Correct Splicing of a Group II Intron from a Chimeric Reporter Gene Transcript in Tobacco Plastids. Nucleic Acids Research 23.13: 2544-2547.

http://www.mendeley.com/research/correct-splicing-group-ii-intron-chimeric-reporter-gene-transcript-tobacco-plastids/

Edited: 12/14/2011