Proceedings of the 56th Italian Society of Agricultural Genetics Annual Congress
Perugia, Italy – 17/20 September, 2012
ISBN 978-88-904570-1-2
Poster Communication Abstract – 7.17
FUNCTIONAL ANALYSIS OF A R2R3-MYB TRANSCRIPTION FACTOR
IN MAIZE
MANZOTTI P.S.*, DALLA VILLA G.*, HORNER D.**, LAROCCA N.***,
SCARAFONI A.****, CONSONNI G.*
*) Dipartimento di Scienze Agrarie e Ambientali – Produzione, Territorio, Agroenergia, Università
degli Studi di Milano, 20133 Milano (Italy)
**) Dipartimento di Bioscienze, Università degli Studi di Milano, 20133 Milano (Italy)
***) Dipartimento di Biologia, Università degli Studi di Padova, 35131 Padova (Italy)
****)Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, Università degli Studi di
Milano, 20133 Milano (Italy)
MYB, transcription factor, maize, epicuticular waxes
The MYB genes constitute one of the largest transcription factor families in plants. They are
characterized by the presence of one to four imperfect MYB repeats (R) that function in DNA
binding and in protein-protein interactions. Each MYB repeat is composed of about 52 amino acid
residues and adopts a helix-turn-helix conformation. Depending on the type and number of repeats,
MYB proteins are classified into different subfamilies; among them, the R2R3-MYB subfamily is
the most abundant in plants. Its members have been intensively studied in the model plants
Arabidopsis, where they have been classified into 22 subgroups, based on the presence of
distinctive motifs outside of the conserved MYB domains. The subgroup1 (S1) comprises
AtMYB30, AtMYB60 and AtMYB96, that are involved in various responses to unfavorable
environmental conditions. AtMYB30 encodes an activator of the hypersensitive cell death program
in response pathogen attack, and both AtMYB60 and AtMYB96 regulate stomatal movement,
drought stress and disease resistance.
The maize Fused leaves1 (fdl1) gene, located on the long arm of chromosome 7, has been
isolated in our laboratory through a forward genetic approach. Its action is confined to the early
stages of plant development, where it promotes germination, through coleoptile opening, as well as
organ separation, through epicuticular waxes deposition. fdl1 putative product is a R2R3-MYB
protein of 330 amino acids that has been ascribed, through phylogenetic analysis, to the S1
subfamily. Sequence similarities as well as functional correspondence have been observed between
this factor and AtMYB30 and AtMYB96, both involved in the biosynthesis of very-long chain fatty
acids that are precursors to epicuticular waxes. However, phylogenetic analysis has not highlighted
a direct ortholog in dicots. This finding suggests that this R2R3-MYB factor is a result of a
diversification event that occurred during the evolution of S1 MYB transcription factors in maize.
To acquire a better understanding of the role exerted during plant development, we have
analyzed the spatial and temporal expression profile by monitoring fdl1 mRNA levels by RT-qPCR
analysis in different tissues, such as embryo, roots, seedlings, leaves, tassels, and ears, at different
developmental time. We will also investigate its expression profile in response to abiotic and biotic
stresses. Moreover, to gain insight into the mechanism of action of this R2R3-MYB protein we aim
to detect the putative target genes, by comparing the expression profile of maize genes implicated in
the biosynthesis and accumulation of epicuticular waxes in mutant and wild-type plants.