Novel marker genes for early leaf development indicate spatial regulation of carbohydrate metabolism within the epical meristem

To identify genes expressed at the earliest stages of leaf development, we have performed a differential display analysis using portions of meristems destined to form leaves. Our analysis led to the identification of five gen es showing an asymmetric pattern of gene expression within the meristem ass ociated with leaf formation. Surprisingly, three of these genes encoded enz ymes involved in carbohydrate metabolism (ADPglucose pyrophosphorylase, suc rose synthase and an SNF1-like kinase). Furthermore, specific transcript pa tterns were responsive to specific sugar and hormonal treatments. The other two genes identified encoded a Phantastica-like myb transcription factor ( associated with the acquisition of leaf dorsiventrality) and CYP85 (a cytoc hrome P450, which plays a pivotal role in brassinolide metabolism). These d ata, firstly, identify a novel set of marker genes for the analysis of the earliest stages of leaf formation. Secondly, the function of the proteins e ncoded by these genes and their expression patterns within the meristem ind icate that carbohydrate metabolism is spatially regulated within a tissue i nvolved in key developmental processes. Finally, our data provide the first indication of an asymmetry in gene expression related to hormone biosynthe sis in the meristem.