Differential Expression of Three BOR1 Genes Corresponding to Different Genomes in Response to Boron Conditions in Hexaploid Wheat (Triticum aestivum L.)

Abstract

Boron (B) is an essential micronutrient for plants. Efflux-type B transporters, BORs, have been identified in Arabidopsis thaliana and rice. Here we identified BOR1 genes encoding B efflux transporters, from the hexaploid genome of wheat (Triticum aestivum L.). We cloned three genes closely related to OsBOR1 and named them TaBOR1.1, TaBOR1.2 and TaBOR1.3. All three TaBOR1s showed B efflux activities when expressed in tobacco BY-2 cells. TaBOR1-green fluorescent protein (GFP) fusion proteins were expressed in Arabidopsis leaf cells localized in the plasma membrane. The transcript accumulation patterns of the three genes differ in terms of tissue specificity and B nutrition responses. In roots, transcripts for all three genes accumulated abundantly while in shoots, the TaBOR1.2 transcript is the most abundant, followed by those of TaBOR1.1 and TaBOR1.3. Accumulation of TaBOR1.1 transcript is up-regulated under B deficiency conditions in both roots and shoots. In contrast, TaBOR1.2 transcript accumulation significantly increased in roots under excess B conditions. TaBOR1.3 transcript accumulation was reduced under excess B. Taken together, these results demonstrated that TaBOR1s are the B efflux transporters in wheat and, interestingly, the genes on the A, B and D genomes have different expression patterns.

Arabidopsis thaliana BOR4is upregulated under high boron conditions and confers tolerance to high boron

“…Among BOR genes in plants, TaBOR1.2 in wheat is reported to be induced under toxic levels of B supply (Leaungthitikanchana et al 2013), although the physiological function of TaBOR1.2 is still unclear. It has been also reported that transcript levels of a homologous gene to BOR (Bot1) is induced by high-B treatment in shoots of Puccinellia distans, an extremely high-B tolerant plant species (Padmanabhan et al 2012).…”

Physiological and genetic responses to boron deficiency inBrassica napus: A review

“…Recently, BOR1 has been reported to have a similar function in other species, including OsBOR1 in rice (Nakagawa et al 2007), TaBOR1 in wheat (Leaungthitikanchana et al 2013), VvBOR1 in grape (Vitis vinifera L.) (Perez-Castro et al 2012) and CmBOR1 in Citrus macrophylla Wester. (Cañon et al 2013).…”

Comparison ofBOR1-like gene expression in two genotypes with different boron efficiencies in commercial crop plants in Thailand

“…Fang60, which is classified as a B-efficient variety (Jamjod et al 1992) and Bonza, which is classified as a B-inefficient variety (Rerkasem et al 1997a) were used in this study. Three BOR1-like genes (named TaBOR1.1, TaBOR1.2 and TaBOR1.3), which is the most similar to OsBOR1 in amino acid sequence, were identified from the wheat genome, and these are functional efflux transporters of B, as was the case for AtBOR1 and OsBOR1 (Leaungthitikanchana et al 2013).…”

“…The sequences of the primers were shown in Table 1. The sequences of TaBOR1.1, TaBOR1.2, TaBOR1.3 is described in previous reports (Leaungthitikanchana et al 2013) The …”