Higher plant chloroplasts provide the only experimentally
validated example of functional tRNA genes that are disrupted
by group II introns. Here, precursor transcripts for tRNAGly(UCC),
tRNAVal(UAC), and tRNAAla(UGC) were
investigated for processing of 5′ leader and 3′
trailer sequences in vivo. Use of intron-specific primer
pairs and inclusion of a barley chloroplast splicing mutant
specifically allowed us to evaluate the potential effect
of intervening sequences that disrupt tRNA secondary and
tertiary structures. The data suggest that (1) neither
integrity of the dihydrouridine nor the anticodon domain
is required for the nucleotidyltransferase-mediated addition
of 3′-terminal CCA; (2) interruption of these two
structural elements by group II introns does not interfere
with nucleotide-specific 5′ maturation by RNase P;
(3) processing intermediates of chloroplast tRNAs can be
3′ polyadenylated; and (4) plastid DNA-encoded proteins
are not required for 3′ and 5′ maturation of
plastid tRNAs.
