Tandem Quadruplication of HMA4 in the Zinc (Zn) and Cadmium (Cd) Hyperaccumulator Noccaea caerulescens

• DOI: 10.1371/journal.pone.0017814
• Publication Date: 2011-03-10T21:59:29Z
• Authors: Seosamh Ó Lochlainn; Helen C. Bowen; Rupert G. Fray; John P. Hammond; Graham J. King; Philip J. White; Neil S. Graham; Martin R. Broadley
• Keywords: Fosmid

Zinc (Zn) and cadmium (Cd) hyperaccumulation may have evolved twice in the Brassicaceae, Arabidopsis halleri Noccaea genus. Tandem gene duplication deregulated expression of Zn transporter, HMA4, has previously been linked to Zn/Cd A. halleri. Here, we tested hypothesis that tandem deregulation HMA4 also occurs Noccaea. A caerulescens genomic library was generated, containing 36,864 fosmid pCC1FOS™ clones with insert sizes ∼20–40 kbp, screened a PCR-generated probe. Gene copy number within genome estimated through DNA fingerprinting pooled pyrosequencing. numbers individual determined by PCR analyses novel locus specific primers. Entire fosmids were then sequenced individually reads equivalent 20-fold coverage assembled generate complete whole contigs. Four repeats identified contiguous sequence 101,480 bp based on overlap identities. These flanked regions syntenous up downstream AtHMA4 thaliana. Promoter-reporter β-glucuronidase (GUS) fusion analysis NcHMA4 thaliana revealed roots shoots, analogous AhHMA4 promoters, but distinct from which localised root vascular tissue. This remarkable consistency metal transport genes between N. halleri, last shared common ancestor >40 mya, provides intriguing evidence parallel evolutionary pathways underlie Brassicaceae.