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 cha racterized by a thin papery lemma from which the grain readily threshe s free, a multiflorous habit, and rachillas that are elongated in comp arison 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 morpholog y in naked and husked oats was shown to diverge early in panicle devel opment: 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 bot h genotypes, though in naked oats it was restricted to the vascular bu ndles. Mature lemmas of the naked genotype closely resembled glumes in appearance and in lignification pattern. Genotypic differences in ext ractable polypeptide complements were apparent only late in developmen t, 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 f actor with properties similar to those of previously-characterized hom eotic gene products in plants.