A maize mutant with an altered vascular pattern

A recessive maize mutant with disrupted seedling development was isolated following transpositional mutagenesis with Mutator. This mutant, initially identified during germination on the basis of abnormal growth of the scutellar node, was designated lsn1 (l arge s cutellar n ode). The mutant seedling exhibits an enlarged primary root with a longitudinal groove and multiple separate root tips. The mutant root is shorter than normal, because of defective cell elongation, and lacks lateral roots. The mutant plant shows defective leaves and reduced internode elongation. Histological analyses on primary root, shoot, scutellar node and juvenile leaves revealed a series of defects, all related to an irregular differentiation of vascular elements. In addition, in situ hybridization of mutant leaves demonstrates an abnormal pattern of expression of Knotted-1, a marker of meristem function. The presence of multiple roots fused together can be interpreted as suppression of the negative control responsible for the differentiation of only one root primordium. Therefore, the data obtained on seedlings of lsn1 point to a relationship between meristem activity, vascular differentiation and auxin polar transport, and may allow the identification of a gene which is active during embryogenesis.