Abstract
srd2 is a temperature-sensitive mutant of Arabidopsis thaliana that were characterized by defects in various tissue culture responses including hypocotyl dedifferentiation and shoot redifferentiation. The SRD2 gene encodes a nuclear protein similar in sequence with human SNAP50, functioning in activation of snRNA transcription.
Analysis with seedlings indicated that SRD2 is strongly expressed in apical meristems, leaf primordia, and central cylinders of roots, which were largely overlapped with expression of U2.3 snRNA promoter-driven reporter gene. The srd2 mutation caused morphological lesions in these region at the restrictive temperature. In the course of lateral root development, snRNAs, which were abundant in young primordia. disappeared at the end of primordium formation, and then increased again. The srd2 mutation disturbed this increase, which was associated with ill establishment of apical meristems. These findings suggested that snRNA transcription activation by SRD2 is required not only for tissue culture responses but also morphogenesis during normal development.
