Heavy metal ATPase 3 expression controls zinc homeostasis in natural accessions of Arabidopsis thaliana

In Arabidopsis thaliana, heavy metal ATPase 3 (AtHMA3) transports zinc (Zn) and other divalent cations into root vacuoles. We have previously shown that AtHMA3 expression variations are buffered by transcriptional changes in the Zn homeostasis network in order to maintain Zn shoot concentration in A. thaliana transgenic lines expressing a functional AtHMA3 allele within a background lacking a functional copy. However, it is unclear whether natural AtHMA3 expression variations are also buffered by similar changes in the expression of Zn transporters. To test this hypothesis, we used A. thaliana accessions that naturally express functional AtHMA3 alleles at different levels and evaluated the expression of genes potentially involved in Zn homeostatic control in different plant root accessions. A significant positive correlation between AtHMA3 expression and the Zn transporter genes AtZIP3 and AtMTP1 was found, suggesting these genes play a role in the previously reported transcriptional buffering. We suggest that this regulation is conserved among the studied natural accessions. However, the lack of correlation between AtHMA3 expression and the other tested genes indicates that only a subset of possible transcriptional buffering pathways are present in natural accessions of A. thaliana, therefore, trade-offs may occur.