The maize (Zea mays) crinkly4 (cr4) gene encodes a receptor-like kinase (RLK). Its mutants show irregularities in the epidermal cells of crinkled and severely adherent leaves, resulting in dwarf characteristics and delayed growth. We successfully grew cr4 mutants up to the reproductive stage, where we noted both pistillate and staminate spikelets in the tassels. This suggests that the cr4 gene may be involved in the sex-determination process during bisexual floral-organ development. We found no remarkable abnormalities in the roots. Northern-blot analysis showed that cr4 gene transcripts were abundant in the leaves, weak in the stems, tassels, and ears, and hardly measurable in the roots. Likewise, transcripts were not detected in the leaves of dark-grown seedling, but were greatly induced after 24 h of light exposure, indicating that expression of the cr4 gene is regulated by light. However, transcripts were not inducible in the roots of seedlings either when grown in the dark or following exposure to light treatment, which suggests that this gene is expressed only in aerial-specific organs.