Novel Insights Into the Hyperaccumulation Syndrome in Pycnandra (Sapotaceae) Sandrine Isnard, Laurent L’huillier, Adrian Paul, Jérôme Munzinger, Bruno Fogliani, Guillaume Echevarria, Peter Erskine, Vidiro Gei, Tanguy Jaffré, Antony van der Ent To cite this version: Sandrine Isnard, Laurent L’huillier, Adrian Paul, Jérôme Munzinger, Bruno Fogliani, et al.. Novel Insights Into the Hyperaccumulation Syndrome in Pycnandra (Sapotaceae). Frontiers in Plant Science, Frontiers, 2020, 11, 10.3389/fpls.2020.559059. hal-02940369 HAL Id: hal-02940369 https://hal.inrae.fr/hal-02940369 Submitted on 16 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. ORIGINAL RESEARCH published: 09 September 2020 doi: 10.3389/fpls.2020.559059 Novel Insights Into the Hyperaccumulation Syndrome in Pycnandra (Sapotaceae) Sandrine Isnard 1,2*, Laurent L’Huillier 3, Adrian L. D. Paul 4,Je´ roˆ me Munzinger 1, Bruno Fogliani 3,5, Guillaume Echevarria 4,6, Peter D. Erskine 4, Vidiro Gei 4, Tanguy Jaffre´ 1,2 and Antony van der Ent 4,6 1 AMAP, Universite´ Montpellier, IRD, CIRAD CNRS, INRAE, Montpellier, France, 2 AMAP, IRD, Herbier de Nouvelle-Cale´ donie, Noume´ a, New Caledonia, 3 Institut Agronomique ne´ o-Cale´ donien (IAC), Equipe ARBOREAL (AgricultuRe BiOdiveRsite´ Et vAlorisation), Paita, New Caledonia, 4 Centre for Mined Land Rehabilitation, Sustainable Minerals Institute, The University of Queensland, St Lucia, QLD, Australia, 5 Institute of Exact and Applied Sciences (ISEA), Université de la Nouvelle-Calédonie, Nouméa, New Caledonia, 6 Universite´ de Lorraine – INRAE, Laboratoire Sols et Environnement, Vandoeuvre-lès-Nancy, France The discovery of nickel hyperaccumulation, in Pycnandra acuminata, was the start of a global quest in this fascinating phenomenon. Despite recent advances in the physiology and molecular genetics of hyperaccumulation, the mechanisms and tolerance of Ni accumulation in the most extreme example reported to date, P. acuminata,remains Edited by: enigmatic. We conducted a hydroponic experiment to establish Ni tolerance levels and Andre Rodrigues dos Reis, São Paulo State University, Brazil translocation patterns in roots and shoots of P. acuminata, and analyzed elemental Reviewed by: partitioning to gain insights into Ni regulation. We combined a phylogeny and foliar Ni Matthew John Milner, concentrations to assess the incidence of hyperaccumulation within the genus Pycnandra. National Institute of Agricultural Botany Hydroponic dosing experiments revealed that P. acuminata can resist extreme Ni (NIAB), United Kingdom Jose´ Lavres Junior, concentrations in solution (up to 3,000 µM), and dosing at 100 µM Ni was beneficial to University of São Paulo, Brazil growth. All plant parts were highly enriched in Ni, but the latex had extreme Ni concentrations *Correspondence: (124,000 µg g−1). Hyperaccumulation evolved independently in only two subgenera and five Sandrine Isnard [email protected] species of the genus Pycnandra. The extremely high level of Ni tolerance is posited to derive from the unique properties of laticifers. The evolutionary and ecological significance of Ni Specialty section: hyperaccumulation in Pycnandra is discussed in light of these findings. We suggest that Ni- This article was submitted to Plant Nutrition, richlaticifersmightbemorewidespreadinthe plant kingdom and that more investigation a section of the journal is warranted. Frontiers in Plant Science Keywords: hydroponic, hyperaccumulation, laticifers, nickel, Pycnandra, X-ray fluorescence spectroscopy Received: 02 June 2020 Accepted: 13 August 2020 Published: 09 September 2020 Citation: INTRODUCTION Isnard S, L’Huillier L, Paul ALD, Munzinger J, Fogliani B, Echevarria G, The seminal report by Jaffréet al. (1976) on the nickel (Ni)-rich latex of Pycnandra acuminata Erskine PD, Gei V, Jaffre´ T and (previously Sebertia acuminata; Sapotaceae) introduced the term “hyperaccumulator” and gave rise van der Ent A (2020) Novel Insights to a new field of research (Jaffréet al., 1976; Jaffréet al., 2018). Hyperaccumulators are unusual plants that Into the Hyperaccumulation Syndrome accumulate metals or metalloids (e.g. Ni, Co, Mn, Zn) in their living tissues to levels that may be in Pycnandra (Sapotaceae). Front. Plant Sci. 11:559059. hundreds or thousands of times greater than what is normal for most plants (Reeves, 2003; van der Ent −1 doi: 10.3389/fpls.2020.559059 et al., 2013). While most plants only contain ≤10 µg g of Ni in their tissues, Ni-hyperaccumulators are Frontiers in Plant Science | www.frontiersin.org1 September 2020 | Volume 11 | Article 559059 Isnard et al. Extreme Nickel Tolerance in Pycnandra − capable of accumulating ≥ 1,000 µg g 1 of Ni in their tissues (Brooks endogenous nitrogen for plant growth (Gerendás et al., 1999). In et al., 1977).Theremarkablesyndromeofhyperaccumulationisa contrast, the exposure of normal plants to elevated Ni concentrations response to the elevated Ni concentrations typically found in soils alterstheuptakeofFeandMgprovokingchlorosis,anddepressing derived from ultramaficrocks(i.e. Mg- and Fe-rich) (Brooks, 1987). plant growth (Tan et al., 2000; Seregin and Kozhevnikova, 2006; Pycnandra acuminata, a large tree endemic to New Caledonia, has Nishida et al., 2011). The critical toxicity level for Ni in normal plants − attracted the attention of scientists for nearly five decades because of isabout10to50µgg1 (Krämer, 2010). Nickel hyperaccumulator its vivid blue-green latex (Figures 1A, D)thatcontainsupto plant species have extraordinarily high levels of resistance and can − 257,000 µg g 1 Ni (Jaffréet al., 1976), the highest Ni concentration tolerate high concentrations of Ni in soil and in solution in ever found in a living organism (Sagner et al., 1998; Rascio and cultivation. In hydroponics experiments, the biomass production Navari-Izzo, 2011). of hyperaccumulators (e.g. Alyssum bertolonii, Noccaea goesingense, Nickel is an essential mineral element for higher plants, even Berkheya coddii) remains unaffected by Ni concentrations of up to though it is usually required in extremely low concentrations several hundred µM in the hydroponic solution (Gabbrielli et al., (Brown et al., 1987). One key function of Ni is as an essential 1991; Krämer et al., 1997; Robinson et al., 2003). component of urease, an enzyme which catalyzes urea hydrolysis Several hypotheses have been put forth to explain the selective for the release of ammonia (Gerendás et al., 1999; Taiz and advantage of the hyperaccumulation syndrome, ranging from Zeiger, 2006). This activity contributes to the recycling of simple sequestration of toxic metals, physiological benefits, FIGURE 1 | Hyperaccumulator species in the genus Pycnandra (Sapotaceae) from New Caledonia. All three species have a blue-green Ni-rich latex. (A) Mature specimen of Pycnandra acuminata with a tree height of approximately 24 m in the Parc de la Rivière Bleue. (B) Individual of P. caeruleilatex in Kuebini, Yate. (C) Individual of P. kouakouensis in Mount Kouakoué. Green-blue Ni-rich latex exuding from the main trunk of Pycnandra acuminata (D), white Ni-poor latex exuding from the main trunk of P. caeruleilatex (E), green-blue Ni-rich latex exuding a small cut branch of P. caeruleilatex (G), green-blue Ni-rich latex exuding a small cut branch and broken petiole of P. kouakouensis in (F–H). Frontiers in Plant Science | www.frontiersin.org2 September 2020 | Volume 11 | Article 559059 Isnard et al. Extreme Nickel Tolerance in Pycnandra drought stress protection, allelopathic effects and “elemental the collection of large datasets. Recent advances in handheld X- defence”. However there is no consensus, and hyperaccumulation ray fluorescence spectroscopy (XRF) systems have enabled non- may have evolved for different reasons in different lineages in the destructive analysis of herbarium specimens (McCartha et al., plant kingdom (Martens and Boyd, 1994; Boyd and Martens, 1998; 2019; van der Ent et al., 2019b), and this approach has been Boyd and Jaffré, 2001; Bhatia et al., 2005). To date, most studies successfully applied to assess the incidence of hyperaccumulation regarding the mechanisms of uptake and tolerance of Ni in the ultramafic flora of New Caledonia (Gei et al., 2020). This hyperaccumulation have been limited to few model herbaceous work has permitted mass measurements of tens of thousands of species (Berkheya (Asteraceae); Noccaea and Alyssum (Brassicaceae)). samples in herbaria in a relatively short time span at low-cost Very little is comparatively known about woody hyperaccumulators (van der Ent et al., 2019a). Another advantage of XRF analysis is that represent a large proportion of the diversity of Ni that the raw data (e.g. energy-dispersive X-ray fluorescence hyperaccumulators in tropical regions of the world (Reeves spectra) can be reprocessed when more accurate calibration et al., 2018). models become available (van der Ent et al., 2019a). In most hyperaccumulator plants studied to date Ni is Here, we combine experimental and field approaches to gain preferentially accumulated in foliar