18th International Symposium on Iron Nutrition and Interaction in Plants
Madrid – May 30-June 3 2016
DISCOVERY
AND
CHARACTERISATION
OF
NICOTIANAMINE
DEOXYMUGINEIC ACID SYNTHASE GENES ESSENTIAL
TO
AMINOTRANSFERASE
STRATEGY II FE UPTAKE
IN
AND
BREAD
WHEAT
Jesse T. Beasley1, Julien P. Bonneau1, Yuan Li2, Alexander A. T. Johnson1*
1School
of BioSciences, The University of Melbourne, Victoria 3010, Australia
Centre for Plant Functional Genomics, University of Adelaide, South Australia, 5064, Australia
*Corresponding author. Tel.: +61 3 8344 3969; fax: +61 3 9347 5460; [email protected]
2Australian
Strategy II iron (Fe) uptake is present in all graminaceous plant species and allows the uptake of essential
ferric (Fe3+) ions from the rhizosphere for use within the plant. Inherent to the function of strategy II are Fechelating molecules known as mugineic acid phytosiderophores (MAs), such as 2’-deoxymugineic acid
(DMA). Genes encoding the two enzymes responsible for DMA biosynthesis – nicotianamine
aminotransferase (NAAT)1,2 and deoxymugineic acid synthase (DMAS)3 – have not yet been described in
bread wheat (Triticum aestivum L.). Here we describe the identification and characterisation of six TaNAAT
and three TaDMAS genes within the bread wheat genome. The coding sequences of TaNAAT homeologs
were composed of seven exons with ≥92.0% nucleotide sequence identity, however, significant variation was
found in the first exon. The coding sequences of TaDMAS homeologs were composed of three exons with
≥97.8% nucleotide sequence identity. Phylogenetic analysis revealed two distinct groups of TaNAAT proteins
closely related to the HvNAATA and HvNAATB proteins of barley. In addition the TaDMAS proteins were
most closely related to the HvDMAS proteins of barley. Expression of the nine wheat genes was investigated
using qRT-PCR analysis of cDNA libraries derived from bread wheat cv. Chinese Spring tissues grown under
Fe sufficient conditions, as well as bread wheat cv. Gladius seedlings exposed to Fe sufficient and deficient
hydroponic growth conditions. The cv. Chinese Spring tissue series analysis revealed that the TaNAATB
genes were specifically expressed in anther tissues, whilst the TaNAATA and TaDMAS genes were
predominantly expressed in root tissues. In the cv. Gladius seedlings, expression of all nine genes was
significantly induced at day 5 in root tissues in response to Fe deficiency relative to Fe sufficient conditions.
Identification and characterization of the TaNAAT and TaDMAS genes in bread wheat could lead to the
development of novel wheat cultivars with increased tolerance to Fe toxicity or deficiency.
Keywords: Nicotianamine Aminotransferase, Deoxymugineic Acid Synthase, Phytosiderophores,
Triticum aestivum L., Iron deficiency
REFERENCES:
1
Takahashi 1999 Plant Phys 121
2
Bashir 2006 Journal of Biol Chem 281:43
3
Inoue 2008 Plant Mol Biol 66
Preference for an ORAL presentation in the ‘Fe acquisition, transport and distribution in plants’ session