A Positive Regulatory Loop between foxi3a and foxi3b Is Essential for Specification and Differentiation of Zebrafish Epidermal Ionocytes

BACKGROUND: Epidermal ionocytes play essential roles in the transepithelial transportation of ions, water, and acid-base balance in fish embryos before their branchial counterparts are fully functional. However, the mechanism controlling epidermal ionocyte specification and differentiation remains unknown. METHODOLOGY/PRINCIPAL FINDINGS: In zebrafish, we demonstrated that Delta-Notch-mediated lateral inhibition plays a vital role in singling out epidermal ionocyte progenitors from epidermal stem cells. The entire epidermal ionocyte domain of genetic mutants and morphants, which failed to transmit the DeltaC-Notch1a/Notch3 signal from sending cells (epidermal ionocytes) to receiving cells (epidermal stem cells), differentiates into epidermal ionocytes. The low Notch activity in epidermal ionocyte progenitors is permissive for activating winged helix/forkhead box transcription factors of foxi3a and foxi3b. Through gain- and loss-of-function assays, we show that the foxi3a-foxi3b regulatory loop functions as a master regulator to mediate a dual role of specifying epidermal ionocyte progenitors as well as of subsequently promoting differentiation of Na(+),K(+)-ATPase-rich cells and H(+)-ATPase-rich cells in a concentration-dependent manner. CONCLUSIONS/SIGNIFICANCE: This study provides a framework to show the molecular mechanism controlling epidermal ionocyte specification and differentiation in a low vertebrate for the first time. We propose that the positive regulatory loop between foxi3a and foxi3b not only drives early ionocyte differentiation but also prevents the complete blockage of ionocyte differentiation when the master regulator of foxi3 function is unilaterally compromised

Two new species of Philodendron (Araceae) from Brazil

Volume: 11Start Page: 102End Page: 10

NOMENCLATURE AND TAXONOMY OF PHILODENDRON HASTATUM K. KOCH & SELLO

ABSTRACT The paper discusses the taxonomy and nomenclature of Philodendron hastatum and aims to clarify the status of some other names often used to name specimens with similar leaf blade shape. A description of the species is provided based on the study of herbarium material

Philodendron rhodospermum Calazans & Sakuragui 2013, sp. nov.

Philodendron rhodospermum Calazans & Sakur., sp. nov. (Figures 1, 2) Philodendron rhodospermum is most similar to Philodendron propinquum Schott (1856: 78), but the former has broader ovate leaves, sometimes slightly asymmetric, fewer primary lateral veins (3–5 pairs), lamina notable thinner with secondary lateral veins prominent in dry material, and reddish seeds. Type: — BRAZIL. Espírito Santo: Santa Teresa, Reserva Biológica Augusto Ruschi, road to Goiapaba-açu, 19° 54’ 26.7” S, 40° 32’ 53.7” W, 24 November 2012, L. S. B . Calazans & R. T. Valadares 213 (holotype: RB!; isotypes: CEPEC!, K!). Herb perennial, hemiepiphytic near the ground. Stem branched; internodes 1.5–5.5(–7.5) cm long, cylindrical, dark green to brownish, matte, drying paler brown, epidermis vertically cracked; flagellar shoots present. Petiole 11.6–16.7 × 1.0– 1.5 cm, sheath 11.0–15.6 × 1.0– 1.5 cm, horizontally splayed, glossy green, apical ligule 0.6–1.1 cm long, acute to narrowly rounded, slightly unequal, unsheathed portion of petiole 0.3–1.5 cm long, adaxially flattened, abaxially rounded; leaf blade 13.0–22.0 × (5.0–) 7.5–13.5 cm, often pendulous from the petiole apex, elliptic to broadly ovate, sometimes slightly asymmetric, apex acuminate to cuspidate, margin entire, base rounded to subcordate, smooth, glossy green on both faces, drying membranaceous to subchartaceous, striated, olive-green to brownish; midrib and primary lateral veins adaxially sunken, abaxially raised, primary lateral veins 3–5 pairs, arising at (30–)45–60º angle from midrib, arcuate to margin, drying prominent and greenish-yellow abaxially, secondary veins discrete, parallel to primary veins, numerous, drying prominent on both surfaces. Inflorescence solitary; peduncle 2.0– 4.5 cm long, cylindrical, striated; spathe 6.0–9.0 cm long, ovate, acuminate (the acumen ca. 1.0 cm long), constriction not evident, externally pale yellow, becoming green in fruit, internally cream, resin canals internally visible; stipe of spadix up to 1.5 cm long; spadix 5.1–6.2(–7.2) cm long, slender; fertile male zone 2.8–3.4 cm long, not obviously exerted in fruit; intermediate sterile zone 0.4–0.55 cm long; female zone 1.7–2.0 cm long; stamens ca. 1.0 mm long, in groups of 4–6, prismatic; intermediate staminodes ca. 1.5 mm long, clavate; gynoecium 1.0–2.0 mm long, ovary flask-shaped, slightly broader than style, 2–3(–4)-locular, multi-ovulated, placentation axile. Juvenile berries pale green. Seeds ca. 1 mm long, fusiform, slightly curved, longitudinally striated, reddish-pink, drying purplish-red to brownish. Phenology: —Collected in flower from September to November and in fruit from September to January. Etymology: —The specific epithet alludes to the remarkable reddish-pink coloration of the seeds (Figure 2b–c), a very useful character for field identification. Distribution and habitat: —Known only from two localities in the Espírito Santo State, Atlantic Forest; 600–850 m elevation. Almost all collections are from REBIO Augusto Ruschi, municipality of Santa Teresa, where the species is common and can be easily found on the edge of the trails. Until now, only one collection outside this area is known, at Pedra de Santa Luzia, municipality of Governador Lindenberg, ca. 70 km distant from Santa Teresa. Both localities are situated in an extension of the Serra da Mantiqueira, suggesting a possible broader area of occurrence along this mountain region. Conservation: —Collections made so far are located in remnants of Atlantic Forest (Figure 3). The fragment at Santa Teresa, in the southern part of Espírito Santo State, is extensive and includes a Federal Conservation Unit (REBIO Augusto Ruschi), which ensures some protection for the species. Moreover, there are contiguous protected fragments in the region, such as the Parque Natural Municipal de São Lourenço. The fragment located at Governador Lindenberg is extremely small and is located outside the conservation area, however it is in an area of high priority for conservation, according to Brazilian federal law (Brasil 2007) (Figure 3). Furthermore, according to the laws of Espírito Santo State (Brasil 2011), this fragment is also inserted in a priority area for conservation of Atlantic Forest named Marilândia, which is important for harbouring threatened and endemic species as well as possible taxa new to science. It also consists of a large area of unprotected fragments that contribute to the connectivity of other priority areas for conservation. Official guidelines for the area include biological inventories of fauna and flora, diagnosis of forest fragments and the creation of new protected areas. The presence of this new Philodendron in the area highlights the importance and urgency of these conservation actions in the state. Due to the lack of ecological data and records we are unable to suggest a conservation status for the species at this moment, which should remain as data deficient for conservation purposes. Paratypes:— BRAZIL. Espírito Santo: Santa Teresa, Reserva Biológica Augusto Ruschi, 24 September 2002, R. R . Vervloet et al. 1036 (MBML!); loc. cit., 03 October 2002, R. R . Vervloet et al. 1150 (MBML!); loc. cit., 29 October 2002, R. R . Vervloet et al. 1309 (MBML!); loc. cit., 09 January 2003, R. R . Vervloet et al. 1672 (MBML!). Additional examined material:— BRAZIL. Espírito Santo: Governador Lindenberg, Pedra de Santa Luzia, 19° 17’ 17” S, 40° 27’ 56” W, 07 November 2007, V . Demuner et al. 4483 (MBML!); Santa Teresa, Reserva Biológica Augusto Ruschi, 19 September 2001, L . Kollmann et al. 4684 (MBML!). Affinities: —According to Grayum’s concepts (1996) of sections in subgenus Pteromischum, Philodendron rhodospermum belongs to section Fruticosa Grayum (1996: 117), displaying proleptic growth, stem branched and shrubby, lack of nodal anchor roots, extensive sheath and solitary inflorescences lacking cataphylls. It is similar to P. propinquum Schott (1856: 78), differing by its broader ovate leaves, often pendulous leaf blade (i.e. the acute angle between petiole and lamina), fewer primary lateral veins and reddish seeds (vs. oblong or ovate-oblong leaves, often erect leaf blade, 5–7 primary lateral veins and pale brown seeds). In dry material of P. rhodospermum the leaves are notable thinner and the numerous secondary lateral veins become prominent, providing a striated appearance to the lamina, which is also useful in separating these species. The new species resembles P. romeroi Grayum (1996: 70), an endemic species of Sierra Nevada de Santa Marta, Colombia. This latter can be distinguished by its appressed climbing habit, larger leaves, stout inflorescences and granular abaxial surface on dry leaves, being a member of section Pteromischum (Schott 1856: 77) Engler (1878: 133). Although the previously listed characters indicate the inclusion of P. rhodospermum in section Fruticosa, its similarity with a member of another section emphasizes the complexity involving classification below subgenus level in Pteromischum, as in the whole genus.Published as part of Calazans, Luana S. B. & Sakuragui, Cassia M., 2013, A new species of Philodendron (Araceae) and a key to Brazilian Atlantic Forest species of P. subgenus Pteromischum, pp. 49-55 in Phytotaxa 94 (2) on pages 50-53, DOI: 10.11646/phytotaxa.94.2.3, http://zenodo.org/record/507224