P pe TAC 1 promotes the horizontal growth of branches in peach trees and is a member of a functionally conserved gene family found in diverse plants species

TAC1 has also been identified as a candidate gene for branch angle control in dicotyledonous species, e.g., in peach trees (Prunus persica).

“However, TAC1 has also been identified as a candidate gene for branch angle control in dicotyledonous species, e.g., in peach trees (Prunus persica; Dardick et al., 2013).”

In trees, fruit and wood production are influenced by crown architecture, and trees with compact crowns are suited for high density cultivation and allow yield increases compared to lines with a wider crown.

“In trees, fruit and wood production are influenced by crown architecture. Trees with compact crowns are suited for high density cultivation andand allow yield increases compared to lines with a wider crown (Dardick et al., 2013).”

The most obvious difference on the sequence level between TAC1 and LAZY1 is an EAR like domain at the C-terminus that is only present in LAZY1.

“The most obvious difference on the sequence level between TAC1 and LAZY1 is an EAR like domain at the C-terminus that is only present in LAZY1 (Dardick et al., 2013).”

The opposing activities of TAC1 and LAZY1 may be explained by affinity of TAC1 and LAZY1 for the same promoter motifs, with LAZY1 likely acting as a repressor through the EAR domain and TAC1 competing with LAZY1 and diminishing repression by LAZY1.

“The opposing activities of these transcription factors may be explained by affinity of TAC1 and LAZY1 for the same promoter motifs. LAZY1 likely acts as a repressor through the EAR domain. TAC1, which lacks the EAR domain, may compete with LAZY1 and diminish repression by LAZY1 (Dardick et al., 2013).”

Phylogenetic analyses and studies of intron-exon structure indicate that LAZY1 is, from an evolutionary perspective, the older gene and TAC1 evolved from LAZY1.

“Phylogenetic analyses and studies of intron–exon structure indicate that LAZY1 is, from an evolutionary perspective, the older gene and TAC1 evolved from LAZY1 (Dardick et al., 2013).”

A knockout of the orthologous gene in Arabidopsis resulted in smaller angles between cauline (i.e., inflorescence) branches and the main inflorescence shoot as well as between rosette branches and the stem.

“A knockout of the orthologous gene in Arabidopsis resulted in smaller angles between cauline (i.e., inflorescence) branches and the main inflorescence shoot as well as between rosette branches and the stem.”

P. persica varieties with a compact growth habit are called broomy or pillar lines and the associated semidominant mutation has been designated as br; the mutation was mapped as an insertion that introduces a premature stop codon in a gene encoding a protein with similarity to the monocot TAC1.

“P. persica varieties that exhibit a compact growth habit are called broomy or pillar lines and the associated semidominant mutation has been designated as br. The mutation was mapped as an insertion that introduces a premature stop codon in a gene encoding a protein with similarity to the monocot TAC1.”

PpeTAC1 has been characterized as a controlling factor of branch angle in peach and CsRAV1 from chestnut has been shown to play a role in seasonal control of proleptic branching.

“Also, PpeTAC1 has been characterized as a controlling factor of branch angle in peach (Dardick et al., 2013) and CsRAV1 from chestnut has been shown to play a role in seasonal control of proleptic branching (Moreno-Cortes et al., 2012).”

The pyramid poplar (Populus nigra 'Italica') develops a phenotype comparable to the broomy or pillar variety of peach, and this poplar growth habit may also be caused by a defect in a poplar ortholog of TAC1.

“The pyramid poplar (Populus nigra ‘Italica’) develops a phenotype comparable to the broomy or pillar variety of peach. This poplar growth habit may also be caused by a defect in a poplar ortholog of TAC1.”