Members of the c1/pl1 Regulatory Gene Family Mediate the Response of Maize Aleurone and Mesocotyl to Different Light Qualities and Cytokinins

Paolo Piazza , Antonia Procissi , Gareth I. Jenkins , and Chiara Tonelli ^*

Dipartimento di Genetica e di Biologia dei Microrganismi, Via Celoria, 26, 20133 Milano, Italy (P.P., A.P., C.T.); and Plant Molecular Science Group, Division of Biochemistry and Molecular Biology, Institute of Biomedical and Life Sciences, Bower Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom (G.I.J.)

^* Corresponding author; email: chiara.tonelli{at}unimi.it.

We investigated the role of transcription factors (R, SN, C1, and PL) in the regulation of anthocyanin biosynthesis by different light qualities (white, red, blue, and ultraviolet) and by cytokinin in maize (Zea mays). We analyzed anthocyanin accumulation, structural gene expression, and regulatory gene expression in the seed aleurone and the seedling mesocotyl. In the mesocotyl, white, blue, and ultraviolet-B light strongly induced anthocyanin accumulation and expression of two key structural genes. In contrast, red light had little effect. Cytokinin enhanced the response to light but was not sufficient to induce anthocyanin accumulation in darkness. Plants with the pl-bol3 allele showed high levels of anthocyanin accumulation in response to light, whereas those with the pl-W22 allele did not, demonstrating the importance of pl1 in the light response. The expression of the pl-bol3 gene, encoding an MYB-related transcription factor, was induced by light and enhanced by cytokinin in a very similar manner to the structural genes and anthocyanin accumulation. Expression of the bHLH (basic helix-loop-helix) Sn1-bol3 gene was stimulated by several light qualities, but not enhanced by cytokinin, and was less well correlated with the induction of anthocyanin biosynthesis. In the aleurone, white, red, and blue light were effective in stimulating anthocyanin accumulation and expression of the MYB-related gene C1. The bHLH R gene was constitutively expressed. We conclude that specific members of the MYB-related c1/pl1 gene family play important roles in the regulation of anthocyanin synthesis in maize in response to different light qualities and cytokinin.

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