Morphological and biochemical characterization of spikelet development in naked oats (Avena sativa)

The dominant gene N-1 in cultivated oats gives rise to a phenotype characterized by a thin papery lemma from which the grain readily threshes free, a multiflorous habit, and rachillas that are elongated in comparison to those of husked oats. This study was undertaken in order to identify the stages at which morphological and biochemical development of naked and husked oats begin to diverge, and to look for correlated differences in gene products (mRNAs and proteins). Spikelet morphology in naked and husked oats was shown to diverge early in panicle development: the first visible difference was premature cessation of growth of the third and subsequent florets in husked oats. Lignin deposition in the lemma occurred later and followed a similar time-course in both genotypes, though in naked oats it was restricted to the vascular bundles. Mature lemmas of the naked genotype closely resembled glumes in appearance and in lignification pattern. Genotypic differences in extractable polypeptide complements were apparent only late in development, coinciding with the onset of lignification, and were not associated with comparable differences in translatable mRNA profiles. The normal (n-1) allele at the naked locus is likely to encode a transcription factor with properties similar to those of previously-characterized homeotic gene products in plants.