At HB 23 participates in the gene regulatory network controlling root branching and reveals differences between secondary and tertiary roots

PEROTTI, MARÍA FLORENCIA; RIBONE, PAMELA ANAHÍ; CABELLO, JULIETA VIRGINIA; ARIEL, FEDERICO DAMIÁN; CHAN, RAQUEL LÍA

PLANT JOURNAL

WILEY-BLACKWELL PUBLISHING, INC

Año: 2019

0960-7412

In Arabidopsis, lateralroot (LR) development is mainly controlled by several known auxin-regulated transcription factors (TFs). Here, we show that AtHB23 (ahomeodomain-leucine zipper I TF) participates in this intricate network. Our study of the expression pattern of AtHB23 revealed that it istranscriptionally activated inthe earlystages of secondary LR primordium. We found that AtHB23 directly limits theexpression of LBD16, a key factor inLR initiation, and also directlyinduces the auxin transporter gene LAX3.We propose that this HD-Zip I mediates the regulation of LAX3 by ARF7/19. Furthermore, AtHB23 plays distinct roles during the formation of secondary andtertiary roots, exhibiting differential expression patterns. ATHB23 is expressed throughout the tertiaryroot primordium, whereas it is restricted to early stages in secondary primordia, likely later repressing LBD16in tertiary LR development and further inhibiting root emergence. Our results suggest that different genetic programs govern the formationof LR primordia from the main or secondary roots, thereby shaping the global dynamic architecture of the rootsystem.