Characterisation of Pt MYB1, an R2R3-MYB from pine xylem.

A cDNA encoding a member of the R2R3-MYB family of transcription factors was cloned from a library constructed from differentiating Pinus taeda (loblolly pine) xylem RNA. This MYB family member, Pinus taeda MYB1 (PtMYB1), was most abundantly expressed in differentiating xylem, as assessed by both ribonuclease protection assays, and by northern blot analysis with poly(A)-enriched RNA. Similar to other plant R2R3-MYB family members, recombinant Pt MYB1 protein was able to bind to AC elements in electrophoretic mobility shift assays (EMSAs).

Involvement of the R2R3-MYB, AtMYB61, in the ectopic lignification and dark-photomorphogenic components of the det3 mutant phenotype.

Overexpression of a pine MYB, PtMYB4, in Arabidopsis caused ectopic lignin deposition and allowed the plants to undergo photomorphogenesis even when they were grown in the dark. The phenotype caused by PtMYB4 overexpression was reminiscent of the previously characterised dark-photomorphogenic mutant, de-etiolated 3 (det3); consequently, we tested the hypothesis that MYB misexpression may explain aspects of the det3 phenotype. We show here that AtMYB61, a member of the Arabidopsis R2R3-MYB family, is misexpressed in the det3 mutant.

Characterisation of a pine MYB that regulates lignification.

A member of the R2R3-MYB family of transcription factors was cloned from a cDNA library constructed from RNA isolated from differentiating pine xylem. This MYB, Pinus taeda MYB4 (PtMYB4), is expressed in cells undergoing lignification, as revealed by in situ RT-PCR. Electrophoretic mobility shift assays (EMSAs) showed that recombinant PtMYB4 protein is able to bind to DNA motifs known as AC elements.