PhD defence by Feixue Liao


Dissecting the F-bZIP Regulated Zinc Deficiency Response in Legumes and Zinc Hyperaccumulators​​​

Zinc (Zn) is an essential micronutrient for all living organisms. However, Zn deficiency is the most widespread crop micronutrient deficiency. Gaining insights into the molecular mechanism of Zn homeostasis can help alleviate the global Zn deficiency problems. In Arabidopsis thaliana, the F group basic leucine zipper (F-bZIP) transcription factors (TFs), bZIP19 and bZIP23, are the central regulators and Zn sensors in the Zn deficiency response, being therefore attractive targets for Zn biofortification.

Legumes and Zn hyperaccumulators can contribute to the Zn biofortification efforts from different angles. Legumes are an important source of proteins and micronutrients and their use is widespread in human diets, while Zn hyperaccumulator species naturally accumulate very high Zn concentration in the shoots. Therefore, the first aim of this thesis was to dissect the molecular mechanism of Zn deficiency response in the model legume, Medicago truncatula. In this context, the M. truncatula F-bZIPs were identified and functionally characterized.

Results showed that, from the two F-bZIPs identified, MtFbZIP1 is the functional homolog of AtbZIP19/23, whereas MtFbZIP2 does not play a role in the Zn deficiency response. The second aim of this thesis was to identify and investigate the F-bZIP TFs in two Zn hyperaccumulator model species from the Brassicaceae family, Arabidopsis halleri and Noccaea caerulescens. Results indicated that AhbZIP23 and NcbZIP19/23 are the functional homologs of AtbZIP19/23 in A. halleri and N. caerulescens, respectively.

In addition, we proposed a role for one AhbZIP19 variant in the Zn hyperaccumulation trait of A. halleri. Taken together, the results support the conservation of the F-bZIP-regulated Zn deficiency response in M. truncatula, A. halleri and N. caerulescens. This work paves the way for Zn biofortification in crops and contributes to the tackling of worldwide Zn deficiency in human diets.

Assessment Committee:
Professor Mark Aarts, Wageningen University, The Netherlands
Assoc. Professor Manuel Gonzalez-Guerrero, Universidad Politécnica de Madrid, Spain
Professor Michael Broberg Palmgren (Chairman), PLEN, University of Copenhagen, DK

Assoc. Professor Ana G.L. Assuncão, PLEN, University of Copenhagen, Denmark

The defence is followed by a reception in meeting room R322/23 on 3rd floor

Everybody is welcome