Vascularization of the <i>Selaginella</i> rhizophore: anatomical fingerprints of polar auxin transport with implications for the deep fossil record

Matsunaga, Kelly K. S.; Cullen, Nevin; Tomescu, Alexandru M. F.

doi:10.1111/nph.14478

Cited by 17 publications

(12 citation statements)

References 57 publications

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“…One of the most consistent and conserved mechanisms in land plant development is the role of auxin as a signal that induces the root pole. As with seed plants, auxin treatment can enhance root fate in Selaginella (Wochok & Sussex, 1974;Matsunaga et al, 2017;this study). In our study, it appeared that auxin-treated dorsal meristems went through an abbreviated rhizophore stage before the transition to root.…”

Section: Discussionmentioning

confidence: 99%

“…This result would suggest that the rhizophore is also induced by auxin. In addition, earlier work showed that the rhizophore transports auxin (and nutrients) in the same direction (acropetal) and at roughly the same rate as mature roots in Selaginella and seed plant roots, exhibiting a shared physiological trait with the adult root (Wochok & Sussex, 1974;Matsunaga et al, 2017). Although we did not detect auxin signaling mechanisms shared exclusively by rhizophores and roots, we did detect a shared cytokinin response that could secondarily affect auxin responses in these meristems through auxin-cytokinin crosstalk (Moubayidin et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

“…The classification of the rhizophore is made further complicated by the great deal of developmental plasticity normally exhibited by Selaginella root and shoot meristems. Angle meristems are present in pairs, with one meristem, either dorsal or ventral, giving rise to a rhizophore depending on the species and the remaining angle meristem typically giving rise to a shoot (Cusick, 1954;Korall & Kenrick, 2002;Weststrand & Korall, 2016;Matsunaga et al, 2017). Although the fates adopted by each of these structures is near absolute in each species, it has been reported that a small percentage of angle meristems adopt alternate root or shoot fates under normal developmental conditions (Cusick, 1954;Wochok & Sussex, 1975).…”

Section: Introductionmentioning

confidence: 99%

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The Selaginella rhizophore has a unique transcriptional identity compared with root and shoot meristems

et al. 2019

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Summary The genus Selaginella resides in an early branch of the land plant lineage that possesses a vasculature and roots. The majority of the Selaginella root system is shoot borne and emerges through a distinctive structure known as the rhizophore, the organ identity of which has been a long‐debated question. The rhizophore of Selaginella moellendorffii – a model for the lycophytes – shows plasticity to develop into a root or shoot up until 8 d after angle meristem emergence, after which it is committed to root fate. We subsequently use morphology and plasticity to define the stage of rhizophore identity. Transcriptomic analysis of the rhizophore during its plastic stage reveals that, despite some resemblance to the root meristem, rhizophore gene expression patterns are largely distinct from both shoot and root meristems. Based on this transcriptomic analysis and on historical anatomical work, we conclude that the rhizophore is a distinct organ with unique features.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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The Selaginella rhizophore has a unique transcriptional identity compared with root and shoot meristems

et al. 2019

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“…This is suggestive for the existence of an auxin independent meristem initiation and branching mechanism. Polar auxin transport mechanisms are conserved as well (Viaene et al, 2013, 2014; Bennett et al, 2014; Bennett, 2015) and clearly have an important impact on the growth of Selaginella species (Wochok and Sussex, 1973, 1974, 1975; Sanders and Langdale, 2013; Matsunaga et al, 2017). However, the inhibition of polar auxin transport is not able to block root branching in Selaginella moellendorffii , which further supports a potential auxin-independent root branching mechanism.…”

Section: Discussionmentioning

confidence: 99%

Root Branching Is Not Induced by Auxins in Selaginella moellendorffii

et al. 2019

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Angiosperms develop intensively branched root systems that are accommodated with the high capacity to produce plenty of new lateral roots throughout their life-span. Root branching can be dynamically regulated in response to edaphic conditions and provides the plants with a soil-mining potential. This highly specialized branching capacity has most likely been key in the colonization success of the present flowering plants on our planet. The initiation, formation and outgrowth of branching roots in Angiosperms are dominated by the plant hormone auxin. Upon auxin treatment root branching through the formation of lateral roots can easily be induced. In this study, we questioned whether this strong branching-inducing action of auxin is part of a conserved mechanism that was already active in the earliest diverging lineage of vascular plants with roots. In Selaginella, an extant representative species of this early clade of root forming plants, components of the canonical auxin signaling pathway are retrieved in its genome. Although we observed a clear physiological response and an indirect effect on root branching, we were not able to directly induce root branching in this species by application of different auxins. We conclude that the structural and developmental difference of the Selaginella root, which branches via bifurcation of the root meristem, or the absence of an auxin-mediated root development program, is most likely causative for the absence of an auxin-induced branching mechanism.

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“…401–418) use a model incorporating developmental and molecular data to generate an enormous range of dicot leaf shapes, leading to the conclusion that leaf development is a self‐organizing process strongly influenced by venation patterns. These kinds of insights into developmental logic can also be applied to paleobotanical questions, as demonstrated by Matsunaga et al . (pp. 419–428), in which the authors draw new connections between the vascular structure of modern lycopods, patterns of auxin transport, and the appearance of these patterns in the fossil record.…”

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confidence: 99%