AUTHOR=Cavallaro Viviana , Maghrebi Moez , Caschetto Mariachiara , Sacchi Gian Attilio , Nocito Fabio Francesco 

TITLE=Sulfur Stable Isotope Discrimination in Rice: A Sulfur Isotope Mass Balance Study

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 13 - 2022

YEAR=2022

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2022.837517

DOI=10.3389/fpls.2022.837517

ISSN=1664-462X

ABSTRACT=The use of sulfur (S) stable isotopes to study S metabolism in plants is still limited by the relatively small number of studies. It is generally accepted that little S stable isotope discrimination occurs during SO42- uptake. However, S metabolism and allocation are expected to produce separations of S stable isotopes among the different plant S pools and organs. In this study, we measured the S isotope composition of the main S pools of rice plants grown under different SO42- availabilities in appropriate closed and open hydroponic-plant systems. The main results indicate that fractionation against 34S occurred during SO42- uptake. Fractionation was dependent on the amount of residual SO42- in the solution, showing a biphasic behavior related to the relative expression of two SO42- transporter genes (OsSULTR1;1 and OsSULTR1;2) in the roots. S isotope separations among S pools and organs were also observed as the result of substantial S isotope fractionations and mixing effects occurring during SO42- assimilation and plant S partitioning.
Since the S stable isotope separations conserve the memory of the physiological and metabolic activities that determined them, we here underline the potential of the 32S/34S analysis for detailed characterization of the metabolic and molecular processes involved in plant S nutrition and homeostasis.