Biology subjects

Verna, C.

Publications and source records attributed to Verna, C..

3 recordsLinked to original sources

bioRxiv2019

Vein Patterning by Tissue-Specific Auxin Transport

Unlike in animals, in plants vein patterning does not rely on direct cell-cell interaction and cell migration; instead, it depends on the transport of the plant signal auxin, which in turn depends on the activity of the PIN-FORMED1 (PIN1) auxin transporter. The current hypotheses of vein patterning by auxin transport propose that in the epidermis of the developing leaf PIN1-mediated auxin transport converges to peaks of auxin level. From those convergence points of epidermal PIN1 polarity, auxin would be transported in the inner tissues where it would give rise to major veins. Here we tested predictions of this hypothesis and found them unsupported: epidermal PIN1 expression is neither required nor sufficient for auxin-transport-dependent vein patterning, whereas inner-tissue PIN1 expression turns out to be both required and sufficient for auxin-transport-dependent vein patterning. Our results refute all vein patterning hypotheses based on auxin transport from the epidermis and suggest alternatives for future tests.

plant biology↗

bioRxiv2019

A dynamic pattern of local auxin sources is required for root regeneration

Following removal of its stem cell niche, the root meristem can regenerate by recruitment of remnant cells from the stump. Regeneration is initiated by rapid accumulation of auxin near the injury site but the source of this auxin is unknown. Here, we show that auxin accumulation arises from the activity of multiple auxin biosynthetic sources that are newly specified near the cut site and that their continuous activity is required for the regeneration process. Auxin synthesis is highly localized and PIN-mediate transport is dispensable for auxin accumulation and tip regeneration. Roots lacking the activity of the regeneration competence factor ERF115, or that are dissected at a zone of low-regeneration potential, fail to activate local auxin sources. Remarkably, restoring auxin supply is sufficient to confer regeneration capacity to these recalcitrant tissues. We suggest that regeneration competence relies on the ability to specify new local auxin sources in a precise spatio-temporal pattern.

plant biology↗

bioRxiv2019

Coordination of tissue cell polarity by auxin transport and signaling

Coordination of polarity between cells in tissues is key to multicellular organism development. In animals, coordination of this tissue cell polarity often requires direct cell-cell interactions and cell movements, which are precluded in plants by a wall that separates cells and holds them in place; yet plants coordinate the polarity of hundreds of cells during the formation of the veins in their leaves. Overwhelming experimental evidence suggests that the plant signaling molecule auxin coordinates tissue cell polarity to induce vein formation, but how auxin does so is unclear. The prevailing hypothesis proposes that GNOM, a regulator of vesicle formation during protein trafficking, positions auxin transporters of the PIN-FORMED family to the correct side of the plasma membrane. The resulting cell-to-cell, polar transport of auxin would coordinate tissue cell polarity and would induce vein formation. Here we tested this hypothesis by means of a combination of cellular imaging, molecular genetic analysis, and chemical induction and inhibition. Contrary to predictions of the hypothesis, we find that auxin-induced vein formation occurs in the absence of PIN-FORMED proteins or any known intercellular auxin transporter, that the residual auxin-transport-independent vein-patterning activity relies on auxin signaling, and that a GNOM-dependent signal that coordinates tissue cell polarity to induce vein formation acts upstream of both auxin transport and signaling. Our results reveal synergism between auxin transport and signaling, and their unsuspected control by GNOM, in the coordination of tissue cell polarity during vein patterning, one of the most spectacular and informative expressions of tissue cell polarization in plants.

plant biology↗