Endosperm Carotenoid Concentrations in Wheat are Better Correlated with PSY1 Transcript Levels than Enzyme Activities

Abstract

Phytoene synthase (PSY) catalyzes a key reaction in the biosynthesis of carotenoids, which are major contributors of grain yellow pigment content (GYPC) in wheat (Triticum spp.). Although quantitative trait loci (QTL) for GYPC have been linked to PSY1 homoeologs in tetraploid and hexaploid wheat, the underlying molecular and biochemical mechanisms for such associations are not well understood. Functional characterization of wheat PSY1 homoeologs indicated that variations in PSY1 homoeolog enzyme activities did not correspond to different levels of GYPC in the wild‐type tetraploid and hexaploid wheat genotypes analyzed. However, a correlation between PSY1 homoeolog expression and carotenoid accumulation in grain endosperm was evident, suggesting that GYPC is at least partially modulated by transcriptional regulation of PSY1 homoeologs in wheat grains. Further promoter analysis of PSY‐A1 homoeologs with diverse expression profiles in three wheat genotypes revealed not only potential motifs for light and hormonal responses but also new candidate cis‐regulatory elements. Overall, the knowledge on the association of PSY1 homoeolog expression and GYPC can be directly applied to breeding tetraploid and hexaploid wheat varieties with desirable carotenoid levels.

Identification of Lycopene epsilon cyclase (LCYE) gene mutants to potentially increase β-carotene content in durum wheat (Triticum turgidum L.ssp. durum) through TILLING

“…In addition, the β-β branch is only controlled by LCYB that converts lycopene into β-carotene [16–19]. Genes involved in carotenoid biosynthesis in tetraploid wheat exhibit expression patterns that reflect the pigments primary functions at light harvesting and as photoprotective compounds in photoactive tissues, thus higher expression is observed in leaves, compared to stems and roots [20, 21]. The overexpression of the LCYB gene or the knockdown in LCYE expression is sufficient to increse total carotenoid and β-carotene content in plants.…”

Psy-E1, located at the same locus as Psy-A1, contributes strong yellowness to durum wheat but may cause yield loss in Japan.

“…In bread wheat, yield was increased in Lr19-containing NILs in various backgrounds in India (Rai et Alternative splicing occurs in Psy-A1 owing to duplication in an exon, producing aberrant transcripts and decreasing the yellow color of endosperm in bread wheat (Howitt et al 2009). Cultivars of durum and bread wheat with strong yellow endosperm had higher Psy1 gene expression (Qin et al 2016). Tissuespeci c expression and overexpression of bacterial PSY genes dramatically increased provitamin A in bread wheat (Wang et al 2014).…”