Submitted to: American Society of Plant Physiologists Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/1999
Publication Date: N/A
Technical Abstract: Physiological and molecular approaches were used to investigate the effect of plant Zn status on several Zn-transport processes and transcript levels of ZNT1, a Zn transport gene isolated from Thlaspi caerulescens, a Zn/Cd hyperaccumulator, and T. arvense, a related nonaccumulator. In Zn sufficient plants, Zn influx in T. caerulescens roots was 5-fold greater compared to T. arvense. This stimulation correlated closely with a greatl increased ZNT1 transcript abundance in T. caerulescens root and shoots. When T. arvense was made Zn deficient, both ZNT1 transcript abundance and the Vmax for root Zn influx were stimulated. In contrast, in T. caerulescens, root Zn transport and transporter gene expression were not affected by Zn deficiency. However, when T. caerulescens was grown on high levels of Zn, a reduction in ZNT1 transcript level and root Zn transport occurred. Thus it appears that in both hyperaccumulating and non-accumulating Thlaspi species, expression of Zn transporters in the roo (and possibly the shoot) and Zn influx are enhanced by lowering the plant Zn status. However, these responses require significantly higher Zn levels both in the growth solution and in the plant for T. caerulescens. These findings indicate that some aspect of the regulatory mechanism(s) linking plant Zn status with Zn acquisition from the soil is altered in T. caerulescens, which contributes to its ability to hyperaccumulate.