<i>Activator</i> Mutagenesis of the <i>Pink scutellum1/viviparous7</i> Locus of Maize

Singh, Manjit; Lewis, Paul E.; Hardeman, Kristine; Bai, Longchuan; Rose, Jocelyn K. C.; Mazourek, Michael; Chomet, Paul; Brutnell, Thomas P.

doi:10.1105/tpc.010249

Cited by 107 publications

(118 citation statements)

References 46 publications

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“…For the carotenoid biosynthetic pathway, we identified two CrtISO (for carotene isomerase) genes in maize on chromosomes 2 and 4, adding to previously isolated pathway genes for PDS (for phytoene desaturase), ZDS (for zetacarotene desaturase), LCYE (for lycopene e-cyclase), and LCYB (for lycopene b-cyclase), all of which are single copy in maize and other grasses (Buckner et al, 1990;Li et al, 1996Li et al, , 2008aLi et al, , 2008bMatthews et al, 2003;Singh et al, 2003;Harjes et al, 2008;Supplemental Table S1). In contrast to two maize CrtISO genes, only one was found in rice, sorghum, and Arabidopsis (Arabidopsis thaliana; Supplemental Table S1; Supplemental Fig.…”

Section: Pathway Gene Families and Chromosome Mappingmentioning

confidence: 99%

Timing and Biosynthetic Potential for Carotenoid Accumulation in Genetically Diverse Germplasm of Maize

2009

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Enhancement of the carotenoid biosynthetic pathway in food crops benefits human health and adds commercial value of natural food colorants. However, predictable metabolic engineering or breeding is limited by the incomplete understanding of endogenous pathway regulation, including rate-controlling steps and timing of expression in carotenogenic tissues. The grass family (Poaceae) contains major crop staples, including maize (Zea mays), wheat (Triticum aestivum), rice (Oryza sativa), sorghum (Sorghum bicolor), and millet (Pennisetum glaucum). Maize carotenogenesis was investigated using a novel approach to discover genes encoding limiting biosynthetic steps in the nutritionally targeted seed endosperm. A combination of bioinformatics and cloning were first used to identify and map gene families encoding enzymes in maize and other grasses. These enzymes represented upstream pathways for isopentenyl diphosphate and geranylgeranyl diphosphate synthesis and the downstream carotenoid biosynthetic pathway, including conversion to abscisic acid. A maize germplasm collection was used for statistical testing of the correlation between carotenoid content and candidate gene transcript levels. Multiple pathway bottlenecks for isoprenoid biosynthesis and carotenoid biosynthesis were discovered in specific temporal windows of endosperm development. Transcript levels of paralogs encoding isoprenoid isopentenyl diphosphate and geranylgeranyl diphosphate-producing enzymes, DXS3, DXR, HDR, and GGPPS1, were found to positively correlate with endosperm carotenoid content. For carotenoid pathway enzymes, transcript levels for CrtISO inversely correlated with seed carotenoid content, as compared with positive correlation of PSY1 transcripts. Since zeaxanthin epoxidase (ZEP) depletes the carotenoid pool in subsequent conversion to abscisic acid, ZEP transcripts were examined. Carotenoid accumulation was found to be inversely associated with ZEP1 and ZEP2 transcript levels. Extension of the maize results using phylogenetic analysis identified orthologs in other grass species that may serve as potential metabolic engineering targets.

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Section: Pathway Gene Families and Chromosome Mappingmentioning

confidence: 99%

Timing and Biosynthetic Potential for Carotenoid Accumulation in Genetically Diverse Germplasm of Maize

2009

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“…RNA isolation and RT-PCR was as previously described (Sawers et al, 2002;Singh et al, 2003). The full-length coding region of ZmHy2 was amplified using primers RS301 (5#-TGCCTCTCTGCTCTTCCCAAGCTC-3#) and ELMSALIREV (5#-CTTGTCGACTATCCATCCACAGCGTCGCCGAC-GAA-3#).…”

Section: Transcript Analysismentioning

confidence: 99%

“…A digoxygenin-labeled DNA fragment was generated as previously described Singh et al (2003) using primers ELM5 (5#-CCCCTGCACGGAGTATTGTTGTC-3#) and ELM6 (5#-CGCCATGCTCC-GCTTCTT-3#).…”

Section: Recombinant Inbred Mappingmentioning

confidence: 99%

TheElm1(ZmHy2) Gene of Maize Encodes a Phytochromobilin Synthase

et al. 2004

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The light insensitive maize (Zea mays) mutant elongated mesocotyl1 (elm1) has previously been shown to be deficient in the synthesis of the phytochrome chromophore 3E-phytochromobilin (PΦB). To identify the Elm1 gene, a maize homolog of the Arabidopsis PΦB synthase gene AtHY2 was isolated and designated ZmHy2. ZmHy2 encodes a 297-amino acid protein of 34 kD that is 50% identical to AtHY2. ZmHY2 was predicted to be plastid localized and was targeted to chloroplasts following transient expression in tobacco (Nicotiana plumbaginifolia) leaves. Molecular mapping indicated that ZmHy2 is a single copy gene in maize that is genetically linked to the Elm1 locus. Sequence analysis revealed that the ZmHy2 gene of elm1 mutants contains a single G to A transition at the 3′ splice junction of intron III resulting in missplicing and premature translational termination. However, flexibility in the splicing machinery allowed a small pool of in-frame ZmHy2 transcripts to accumulate in elm1 plants. In addition, multiple ZmHy2 transcript forms accumulated in both wild-type and elm1 mutant plants. ZmHy2 splice variants were expressed in Escherichia coli and products examined for activity using a coupled apophytochrome assembly assay. Only full-length ZmHY2 (as defined by homology to AtHY2) was found to exhibit PΦB synthase activity. Thus, the elm1 mutant of maize is deficient in phytochrome response due to a lesion in a gene encoding phytochromobilin synthase that severely compromises the PΦB pool.

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“…Mutants vp1 and possibly rea, referred to as response mutants (class 1), define genes not impaired in ABA biosynthesis. Class 2 includes mutants associated with reduced or suppressed carotenoid accumulation in both endosperm and vegetative tissues (vp2, vp5, vp7, vp9, vp12, al1, y9 and w3) as a result of a mutational block in early biosynthetic steps before the branching point that separates ABA and carotenoid biosynthesis (Singh et al, 2003). Class 3 includes vp8 and vp14 which affect later steps of the biosynthesis (Schwartz et al, 1997) as well as vp10 and vp15 that regulate the synthesis of the molybdenum cofactor required for the last step in ABA biosynthesis (Porch et al, 2006;Suzuki et al, 2006).…”

Section: Introductionmentioning

confidence: 99%

Vivipary as a tool to analyze late embryogenic events in maize

et al. 2008

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In maize vivipary, the precocious germination of the seed while still attached to the ear, is the diagnostic phenotype of mutants, which are impaired in the biosynthesis or response to abscisic acid (ABA). Of the 15 genes so far described, 12 control specific steps in ABA biosynthesis, two mediate hormone response and one still has an undefined role. We have analyzed a collection of 25 independent vp isolates with the aim of determining the degree of mutational saturation that has so far been reached. Of the 25 viviparous mutants complementation tested, 22 correspond to known loci: six are allelic to vp1, another six to vp5, one to vp7, two to vp9, six to vp10 and one to w3. The remaining three represent genes not previously identified. All mutants so far tested except rea show a decrease in ABA content. As to the only two mutants (vp1 and rea) whose endogenous ABA content is not impaired, the reduction in sensitivity of the double mutant compared to the single ones suggests that the two genes control separate pathways in the ABA signal transduction. Some of the mutants in this collection have a characteristic incomplete germination that allows the embryo of the mature dry seed to resume germination. By exploiting this feature it is possible to infer, through a germination test, whether the mutant has been impaired in the acquisition of desiccation tolerance. This information provides the starting point for the dissection of the genetic basis of desiccation tolerance.

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Activator Mutagenesis of the Pink scutellum1/viviparous7 Locus of Maize

Cited by 107 publications

References 46 publications

Timing and Biosynthetic Potential for Carotenoid Accumulation in Genetically Diverse Germplasm of Maize

Timing and Biosynthetic Potential for Carotenoid Accumulation in Genetically Diverse Germplasm of Maize

TheElm1(ZmHy2) Gene of Maize Encodes a Phytochromobilin Synthase

Vivipary as a tool to analyze late embryogenic events in maize

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