Clusters of genes encoding fructan biosynthesizing enzymes in wheat and barley

Abstract

Fructans are soluble carbohydrates with health benefits and possible roles in plant adaptation. Fructan biosynthetic genes were isolated using comparative genomics and physical mapping followed by BAC sequencing in barley. Genes encoding sucrose:sucrose 1-fructosyltransferase (1-SST), fructan:fructan 1-fructosyltransferase (1-FFT) and sucrose:fructan 6-fructosyltransferase (6-SFT) were clustered together with multiple copies of vacuolar invertase genes and a transposable element on two barley BAC. Intron-exon structures of the genes were similar. Phylogenetic analysis of the fructosyltransferases and invertases in the Poaceae showed that the fructan biosynthetic genes may have evolved from vacuolar invertases. Quantitative real-time PCR was performed using leaf RNA extracted from three wheat cultivars grown under different conditions. The 1-SST, 1-FFT and 6-SFT genes had correlated expression patterns in our wheat experiment and in existing barley transcriptome database. Single nucleotide polymorphism (SNP) markers were developed and successfully mapped to a major QTL region affecting wheat grain fructan accumulation in two independent wheat populations. The alleles controlling high- and low- fructan in parental lines were also found to be associated in fructan production in a diverse set of 128 wheat lines. To the authors' knowledge, this is the first report on the mapping and sequencing of a fructan biosynthetic gene cluster and in particular, the isolation of a novel 1-FFT gene from barley.

Wheat stem reserves and salinity tolerance: molecular dissection of fructan biosynthesis and remobilization to grains

“…Up-regulation of 1-SST and 6-SFT along with fructan accumulation were observed in Bam under salinity, at anthesis, whereas down-regulation of 1-SST and 6-SFT in conjunction with fructan depletion were observed in Ghods. Several reports state that these genes are critical for fructan biosynthesis because they are soluble linear or branched polymers of fructose that produce graminan-type fructan and cooperate with 1-FFT gene in wheat ( Van den Ende et al 2003;Livingston et al 2009;Huynh et al 2012). Up-regulation of 1-SST and 6-SFT has been reported under drought stress and positively correlated with the total stem WSCs and fructan content (Xue et al 2008).…”

Optical and physical mapping with local finishing enables megabase-scale resolution of agronomically important regions in the wheat genome

“…One of the 2.5 Mb regions that was finished overlapped the QTL initially defined by Huynh et al (16) for fructan content in the grain and in our analysis was shown to contain a tandem array of seven glycoside hydrolases (EC 3.2.1, labelled a to g) that were of particular interest since the gene model GH32b could be assigned to 1-FFT on sequence similarity basis and GH32g to 6-SFT. Both these genes are key in the fructan biosynthetic pathway (29).…”

“…6D, increased read coverage at centromere end of 7AL indicated by a dotted blue box); the duplication is absent from a standard chromosome 7A. 16 The active centromere and associated kinetochore complex in plants can also be defined based on the location of the CENH3 binding domain (26). We aligned CENH3 ChIP-Seq data for wheat (25,26) to the IWGSC RefSeq v1.0 and found a 5 Mb region on the proximal side of 7AL to the breakpoints (not in the region of overlap between the 7AS and 7AL assemblies) as the primary source of similarity to the CENH3 binding sequences and CRW repeat sequence families (Fig.…”

Fructan synthesis, accumulation and polymer traits. II. Fructan pools in populations of perennial ryegrass (Lolium perenne L.) with variation for water-soluble carbohydrate and candidate genes were not correlated with biosynthetic activity and demonstrated constraints to polymer chain extension

“…Gene duplications and their subsequent divergence can play an important role in the evolution of novel gene functions (Innan and Kondrashov, 2010 ). It has been proposed that the multiple copies of invertase genes and the variants of fructosyltransferase genes in perennial ryegrass arose during evolution from a common cereal ancestor invertase by gene duplication and rearrangement (Francki et al, 2006 ) and such genes can be clustered within the genome (Huynh et al, 2012 ). The recent discoveries of further duplication of fructosyltransferase genes would therefore be excellent candidates for a major role in regulating fructan and WSC content.…”

“…It is possible that this enzyme has a role in fructan synthesis addition to the fructosyltransferases, as proposed by Lothier et al ( 2007 ). TaMYB(myeloblastosis)13 transcription factors from wheat have recently been demonstrated to be activators of fructosyltransferase genes (Xue et al, 2011 ; Huynh et al, 2012 ); to regulate fructosyltransferases (McIntyre et al, 2012 ) and to regulate the fructan biosynthetic pathway leading to enhanced fructan accumulation (Kooiker et al, 2013 ).…”