Abiotic stress modulates root patterning via ABA-regulated microRNA expression in the endodermis initials

Area of Science:

• Plant Biology
• Molecular Plant Physiology
• Developmental Biology

Background:

• Root xylem patterning into protoxylem (PX) and metaxylem is crucial for water transport.
• This process is known to be regulated by auxin-cytokinin signaling and microRNA miR165a/166b-mediated suppression of HD-ZIPIII genes.

Purpose of the Study:

• To investigate the role of abscisic acid (ABA) in regulating root xylem patterning.
• To elucidate the molecular mechanisms by which ABA influences xylem differentiation and lateral root development.

Main Methods:

• Utilized Arabidopsis and tomato models to study osmotic stress and ABA signaling.
• Analyzed gene expression patterns, including VND7, miR165a/166b, ZLL, and HD-ZIPIII family members.
• Employed genetic mutants (phb1-d, scr, shr) to confirm the role of specific genes and pathways.

Main Results:

• Osmotic stress and ABA signaling in meristematic endodermal cells induce PX differentiation, associated with increased VND7 expression.
• ABA enhances PX differentiation in both radial and longitudinal axes in a conserved manner across species.
• ABA increases miR165a/166b expression and reduces ZLL levels, leading to decreased HD-ZIPIII RNA levels.
• ABA-induced inhibition of lateral root development is linked to increased miR165a levels in endodermal precursors and reduced HD-ZIPIII levels.

Conclusions:

• ABA acts as a key regulator of root xylem patterning and maturation through the miR165a/166b-HD-ZIPIII regulatory module.
• ABA signaling influences both primary xylem development and lateral root initiation, highlighting its broad role in root morphogenesis.