Potential role of tRNAs in wheat and Lolium mitochondrial rps7 transcript processing

Area of Science:

• Plant Molecular Biology
• Mitochondrial Genetics
• Gene Expression Regulation

Background:

• The wheat mitochondrial gene encoding ribosomal protein S7 (rps7) produces multiple transcripts.
• These transcripts share a common 3' terminus but differ in length due to 5' end maturation.
• Understanding transcript processing is crucial for deciphering gene expression in plant mitochondria.

Purpose of the Study:

• To investigate the processing events and origins of wheat mitochondrial rps7 transcripts.
• To explore the role of flanking sequences in transcript maturation.
• To compare rps7 transcript characteristics in wheat with those in other grasses.

Main Methods:

• Analysis of wheat mitochondrial rps7 transcripts using Northern blotting and RNA mapping techniques.
• Identification of precursor RNA mapping to a chloroplast-origin tRNA-Phe gene.
• Comparison of transcript structures and origins in wheat and Lolium multiflorum.

Main Results:

• Wheat rps7 transcripts range from 3.4 to 0.7 kb, with 5' end maturation events determining length.
• The longest precursor RNA maps to a chloroplast-derived tRNA-Phe gene, suggesting its role in cleavage.
• Transcript levels and RNA editing differ between seedlings and germinating embryos; Lolium multiflorum rps7 also shows tRNA gene mapping at the 5' terminus.

Conclusions:

• Plant mitochondrial transcription units exhibit significant plasticity.
• Chloroplast-origin sequences are recruited for the expression of mitochondrial genes, such as rps7.
• Tandem tRNA genes play a role in the processing and expression of mitochondrial genes in grasses.