Plant Growth Regulation

, Volume 16, Issue 1, pp 73–81

Variations in the levels of aminoacylation and modified nucleotide content between total tRNAs from chloroplasts and etioplasts in cucumber cotyledons

Authors

  • Chelliah Jayabaskaran
    • Department of BiochemistryIndian Institute of Science
  • Shailaja Hande
    • Department of BiochemistryIndian Institute of Science
Article

DOI: 10.1007/BF00040510

Cite this article as:
Jayabaskaran, C. & Hande, S. Plant Growth Regul (1995) 16: 73. doi:10.1007/BF00040510

Abstract

Total tRNAs isolated from chloroplasts and etioplasts of cucumber cotyledons were compared with respect to amino acid acceptance, isoacceptor distribution and extent of modification. Aminoacylation of the tRNAs with nine different amino acids studied indicated that the relative acceptor activities of chloroplast total tRNAs for four amino acids are significantly higher than etioplast total tRNAs. Two dimensional polyacrylamide gel electrophoresis (2D-PAGE) of chloroplast total tRNAs separated at least 32 spots, while approximately 41 spots were resolved from etioplast total trNAs. Comparison of the reversed-phase chromatography (RPC-5) profiles of chloroplast and etioplast leucyl-, lysyl-, phenylalanyl-, and valyl-tRNA species showed no qualitative differences in the elution profiles. However, leucyl-, lysyl- and valyl-tRNA species showed quantitative differences in the relative amounts of the isoaccepting species present in chloroplasts and etioplasts. The analysis of modified nucleotides of total tRNAs from the two plastid types indicated that total tRNA from etioplasts was under-modified with respect to ribothymidine, isopentenyladenosine/hydroxy-isopentenyladenosine, 1-methylguanosine and 2-o-methylguanosine. This indicates that illumination may cause de novo synthesis of chloroplast tRNA-modifying enzymes encoded for by nuclear genes leading to the formation of highly modified tRNAs in chloroplasts. Based on these results, we speculate that the observed decrease in levels of aminoacylation, variations in the relative amounts of certain isoacceptors, and differences in the electrophoretic mobilities of some extra tRNA spots in the etioplast total tRNAs as compared to chloroplast total tRNAs could be due to some partially undermodified etioplast tRNAs. Taken together, the data suggested that the light-induced transformation of etioplasts into chloroplasts is accompanied by increases in the relative levels of some functional chloroplast tRNAs by post transcriptional nucleotide modifications.

Key words

cucumber chloroplastisoaccepting tRNAlight regulationmodified nucleotidetRNA aminoacylation

Abbreviations

2D-PAGE

two dimensional polyacrylamide gel electrophoresis

RPC-5

reversed phase chromatography

2D-TLC

two dimensional thin layer chromatography

pseudouridine 5′-phosphate

pD

dihydrouridine 5′-phosphate

pT

ribothymidine 5′-phosphate

pm1A

1-methyladenosine 5′-phosphate

pm2A

2-methyladenosine 5′-phosphate

pi6A

N6-isopentenyladenosine 5′-phosphate

pio6A

N6-hydroxyisopentenyladenosine 5′-phosphate

pm5C

5-methylcytidine 5′-phosphate

pCm

O2-methylcytidine 5′-phosphate

pGm

O2-methylguanosine 5′-phosphate

pm1G

1-methylguanosine 5′-phosphate

pm2G

2-methylguanosine 5′-phosphate

pm7G

7-methylguanosine 5′-phosphate

pUm

O2-methyluridine 5′-phosphate

Download to read the full article text

Copyright information

© Kluwer Academic Publishers 1995