AUTHOR=Isnard Sandrine , L’Huillier Laurent , Paul Adrian L. D. , Munzinger Jérôme , Fogliani Bruno , Echevarria Guillaume , Erskine Peter D. , Gei Vidiro , Jaffré Tanguy , van der Ent Antony 

TITLE=Novel Insights Into the Hyperaccumulation Syndrome in Pycnandra (Sapotaceae)

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 11 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.559059

DOI=10.3389/fpls.2020.559059

ISSN=1664-462X

ABSTRACT=The discovery of nickel hyperaccumulation, in Pycnandra acuminata, was the start of a global quest in this fascinating phenomenon. Despite recent advances in physiology and molecular genetics of hyperaccumulation, the mechanisms and tolerance of Ni accumulation in the most extreme example reported to date, P. acuminata, remains enigmatic. 
We conducted a hydroponic experiment to establish Ni tolerance levels and translocation pattern in roots and shoots of P. acuminata, and analysed elemental partitioning to gain insight into Ni regulation. We combined a phylogeny and foliar Ni concentrations to assess the incidence of hyperaccumulation within the genus Pycnandra. 
Hydroponic dosing experiments revealed that P. acuminata can resist extreme Ni concentrations in solution (up to 3000 μM), and dosing at 100 μM Ni was beneficial to growth. All plant parts were highly enriched in Ni, but the latex had extreme Ni concentration (124 000 µg g-1). Hyperaccumulation evolved independently in only two subgenera and five species. 
The extremely high level of Ni tolerance is posited to derive from the unique properties of laticifers. The evolutionary and ecological significance of Ni hyperaccumulation in Pycnandra is discussed in light of these findings. We suggest that Ni-rich laticifers might be more widespread and that more investigation is warranted.