Formation of polarity convergences underlying shoot outgrowths

Abstract

The development of outgrowths from plant shoots depends on formation of epidermal sites of cell polarity convergence with high intracellular auxin at their centre. A parsimonious model for generation of convergence sites is that cell polarity for the auxin transporter PIN1 orients up auxin gradients, as this spontaneously generates convergent alignments. Here we test predictions of this and other models for the patterns of auxin biosynthesis and import. Live imaging of outgrowths from kanadi1 kanadi2 Arabidopsis mutant leaves shows that they arise by formation of PIN1 convergence sites within a proximodistal polarity field. PIN1 polarities are oriented away from regions of high auxin biosynthesis enzyme expression, and towards regions of high auxin importer expression. Both expression patterns are required for normal outgrowth emergence, and may form part of a common module underlying shoot outgrowths. These findings are more consistent with models that spontaneously generate tandem rather than convergent alignments.DOI: http://dx.doi.org/10.7554/eLife.18165.001

Vein Patterning by Tissue-Specific Auxin Transport

“…In conclusion, vein patterning hypotheses based on polar auxin transport from the epidermis (reviewed in (Runions, Smith, & Prusinkiewicz, 2014;Prusinkiewicz & Runions, 2012); see also (Alim & Frey, 2010;Hartmann et al, 2019), and references therein) are unsupported by experimental evidence. Our results do not rule out an influence of the epidermis on vein patterning, for example through local auxin production (e.g., (Abley, Sauret-Gueto, Maree, & Coen, 2016)), but they do exclude that such influence is brought about by polar auxin transport.…”

Ectopic KNOX Expression Affects Plant Development by Altering Tissue Cell Polarity and Identity

“…BKn3 could initially stimulate the formation of a minus organizer, causing the reorientation of polarity toward it. The possible molecular basis of the organizer would depend on the mechanism for coordinating tissue cell polarity (Abley et al, 2016). If auxin is a component of tissue cell polarity, BKn3 could generate a localized increase in intracellular auxin, for example, through enhancing auxin biosynthesis, as suggested by Bolduc et al (2012).…”

“…Several models have been proposed for how PIN1 may be involved in the establishment of tissue cell polarity: (1) Up-thegradient (Jönsson et al, 2006;Smith et al, 2006), (2) With-the-flux model (Sachs, 1969(Sachs, , 1981Mitchison, 1980;Mitchison et al, 1981;Stoma et al, 2008), and (3) Indirect cell-cell coupling (Abley et al, 2013). With all of these models, coordination of cell polarity across a tissue can be achieved through modulating auxin dynamics (Abley et al, 2016). Analysis of PIN1 localization and class 1 KNOX gene expression in meristems and compound leaves has led to the suggestion that KNOX expression confers competency for PIN1 convergence point formation (Barkoulas et al, 2008;Hay and Tsiantis, 2010), indicating that class 1 KNOX genes and tissue cell polarity may interact.…”

Auxin Acts through MONOPTEROS to Regulate Plant Cell Polarity and Pattern Phyllotaxis

“…The plant hormone auxin plays a central role in establishing these patterns by promoting organ formation at sites where it accumulates due to its polar, cell-to-cell transport [2, 3, 4, 5, 6]. Although experimental evidence as well as modeling suggest that feedback from auxin to its transport direction may help specify phyllotactic patterns [7, 8, 9, 10, 11, 12], the nature of this feedback remains unclear [13]. Here we reveal that polarization of the auxin efflux carrier PIN-FORMED 1 (PIN1) is regulated by the auxin response transcription factor MONOPTEROS (MP) [14].…”