The restriction patterns from juvenile and rejuvenated shoots were identical but differed from the mature pattern. I fragments of 3.6 and 4 Kb from adult mtDNA were cloned and used as probes to confirm the RFLP differences. A search of the mtDNA database with the complete sequence of the 4 Kb fragment failed to shed any light on its possible function, and sequencing of the 3.6 Kb fragment had not been completed. Huang stated, however, that she has observed large shifts in activities of protein kinase and other enzymes associated with the rejuvenation cycle. Peach has an Arabidopsis -size genome of about 265 Mb and a generation time of 2 years.
Work is underway to clone the transposable element for use as a transposon tag.
Much effort has been directed toward improving wood quality by genetic engineering of its lignin component. A common research method is to create anti-sense constructs for enzymes in the lignin biosynthetic pathway and monitor transgenic plants for changes in lignin levels and composition. He pointed out that data from these studies are revealing shortcomings in our understanding of the lignin biosynthetic pathway. In contrast, the PAL I constructs gave little expression in the leaf vasculature, but some expression in the sub-epidermal layer. Northern analysis of poplar leaf transcripts revealed seasonal variations in the expression of both gene families in field-grown trees.