Assessing the Role of Carotenoid Cleavage Dioxygenase 4 Homoeologs in Carotenoid Accumulation and Plant Growth in Tetraploid Wheat

Abstract

The dietary needs of humans for provitamin A carotenoids arise from their inability to synthesize vitamin A de novo. To improve the status of this essential micronutrient, special attention has been given to biofortification of staple foods, such as wheat grains, which are consumed in large quantities but contain low levels of provitamin A carotenoids. However, there remains an unclear contribution of metabolic genes and homoeologs to the turnover of carotenoids in wheat grains. To better understand carotenoid catabolism in tetraploid wheat, Targeting Induced Local Lesions in Genomes (TILLING) mutants of CCD4, encoding a Carotenoid Cleavage Dioxygenase (CCD) that cleaves carotenoids into smaller apocarotenoid molecules, were isolated and characterized. Our analysis showed that ccd4 mutations co-segregated with Poltergeist-like (pll) mutations in the TILLING mutants of A and B subgenomes, hence the ccd-A4 pll-A, ccd-B4 pll-B, and ccd-A4 ccd-B4 pll-A pll-B mutants were analyzed in this study. Carotenoid profiles are comparable in mature grains of the mutant and control plants, indicating that CCD4 homoeologs do not have a major impact on carotenoid accumulation in grains. However, the neoxanthin content was increased in leaves of ccd-A4 ccd-B4 pll-A pll-B relative to the control. In addition, four unidentified carotenoids showed a unique presence in leaves of ccd-A4 ccd-B4 pll-A pll-B plants. These results suggested that CCD4 homoeologs may contribute to the turnover of neoxanthin and the unidentified carotenoids in leaves. Interestingly, abnormal spike, grain, and seminal root phenotypes were also observed for ccd-A4 pll-A, ccd-B4 pll-B, and ccd-A4 ccd-B4 pll-A pll-B plants, suggesting that CCD4 and/or PLL homoeologs could function toward these traits. Overall, this study not only reveals the role of CCD4 in cleavage of carotenoids in leaves and grains, but also uncovers several critical growth traits that are controlled by CCD4, PLL, or the CCD4-PLL interaction.

Enhanced resistance to heat and fungal infection in transgenic Trichoderma via over-expressing the HSP70 gene

“…In addition, several genes involved in glutathione (Yamazaki et al 2019 ), carotenoid (Yu and Tian. 2021 ), ascorbate (Munir et al 2020 ), unsaturated fatty acid biosynthesis (Xue et al 2020 ) and phenylalanine metabolism (Xu and Zhang. 2020 ) were significantly activated in the transgenic strains.…”

“… 2021 ), ascorbate (Munir et al 2020 ), unsaturated fatty acid biosynthesis (Xue et al 2020 ) and phenylalanine metabolism (Xu and Zhang. 2020 ) were significantly activated in the transgenic strains. These results indicated that TvHSP70 over-experssion triggered enzymatic and non-enzymatic anti-oxidant defence mechanisms in Tv-1511 to cope with adverse conditions.…”

A multi-omic resource of wheat seed tissues for nutrient deposition and improvement for human health

“…Thereafter, increasing efforts have been made in the basic and applied research areas to understand the genetic basis of wheat quality, especially the nutritional quality traits, and to genetically improve these traits 4 , 5 . For example, several key enzymes in the carotenoid biosynthetic pathway have been functionally studied, including β-hydroxylase (HYD) 6 , lycopene epsilon cyclase (LCYε) 7 , carotenoid cleavage dioxygenases (CCD) 8 and aldehyde oxidase (AO) 9 , 10 , and transgenic wheat lines or mutant lines have been investigated to discover their effects on biofortification of β-carotene in wheat 11 – 15 . More recently, owing to the technological advances in metabolomics ( e.g ., the widely targeted metabolomics based on ultra-performance liquid chromatography- electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS) 16 ), large-scale identification and quantification of phytochemicals in wheat seeds has become possible.…”