sentence: These results indicate that dark-induced degradation of chlorophyll is more rapid in xrn4 than WT and stable transformation of the mutant with a genomic copy of XRN4 is sufficient to correct this deficiency.Finding that transcripts responding to carbohydrates were among XRN4 substrates , we examined polyadenylated mRNA levels of sugar-starvation responsive marker genes , bZIP1 ( 92 ) and ATL8 ( 93 ) , in dark-treated seedlings ( Figure 6D ) .