Table II.

In vivo conversion of tracer amounts of [³⁵S]Met to [³⁵S]SMM by leaf tissues of wild-type and mmt mutant Arabidopsis and maize

Genotype	[35S]SMM	35S-Labeled Protein	[35S]Met Remaining
	nCi
Arabidopsis wild type	50 ± 8	132 ± 13	142 ± 4
Arabidopsis mmt mutant	<0.4a	112 ± 17	154 ± 7
Maize wild type	84 ± 26	147 ± 27	340 ± 26
Maize mmt mutant	0.8 ± 0.2b	150 ± 10	437 ± 15

Sets of three Arabidopsis leaves or single 25-mm maize leaf segments were supplied with 1.0 μCi (120–130 pmol) of [³⁵S]Met for 1.5 or 2 h in the light and then washed in 0.1 mm Met for 0.5 h to remove unabsorbed label. This [³⁵S]Met dose is very small compared with endogenous free Met content (Ranocha et al., 2001). At least 80% of the [³⁵S]Met was absorbed. Data are expressed as nCi per three leaves (Arabidopsis) or per segment (maize) and are means of three replicates ± se.

^aThe detection limit was 0.4 nCi. 

^bThe identity of the trace of [³⁵S]SMM in mmt mutant maize was confirmed by comigration with authentic SMM in three thin-layer separatory systems and by decomposition in hot base.