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Summary: tdy1 is a recessive mutation that results in leaf blades developing chlorotic, nonclonal regions that hyperaccumulate carbohydrates. Expression of the phenotype is dependent on growth in high light. The chlorotic regions appear soon after a leaf emerges from the whorl and stable once formed. tdy1 is proposed to function in the same genetic pathway as tdy2 based on their nearly identical mutant phenotypes and a dosage-sensitive genetic interaction between the loci (Baker and Braun, 2008). tdy1 appears to be a grass-specific gene that encodes a novel, predicted membrane-localized protein (Ma et al., 2009). tdy1 RNA is expressed in phloem cells in mature and immature leaves, stems and developing ears. tdy1 RNA accumulates in protophloem sieve elements upon differentiation and is one of the earliest phloem-expressed genes reported in maize. tdy1 is hypothesized to function as an osmotic stress or sugar sensor that prevents the over accumulation of carbohydrates in developing leaves.
Images: Leaf of tdy1, courtesy Frank Baker and David Braun.
First reported: Braun et al. (2006)
Key Alleles
tdy1-Reference (tdy1-R): recessive, EMS-induced, proline to arginine substitution at the 112th amino acid.
tdy1-D190: recessive, Mu1 insertion in the 5'UTR 101 base pairs upstream of the ATG.
tdy1-D24: recessive, Mu1 insertion in the 5'UTR 85 base pairs upstream of the ATG.
tdy1-D46: recessive, Mu3 insertion in the 5'UTR 85 base pairs upstream of the ATG.
tdy1-Uniform Mu (tdy1-UMu): recessive, Mu8 insertion in the proximal promoter 177 base pairs upstream of the ATG.
tdy1-PM: recessive, single base pair deletion causing a frame shift mutation at the 200th amino acid and resulting in premature termination.
tdy1-shadow: recessive, a 453 base pair deletion removing the 3' end of the coding sequence and part of the 3' UTR.
tdy1-D6: recessive, a ~180 kb deletion of the entire locus. Viable but sterile due to deletion of afd1. Fully transmissible through male and female gametes (Golubovskaya et al. 2006).
Map Location
Based on tight linkage to afd1 (Golubovskaya et al. 2006).
Gene Product
Encodes a novel protein predicted to localize to a membrane and to be involved in carbohydrate export from leaves Contains a domain of unknown function in the C terminus. (DUF761, pfam05553).
Expression
Phenotypic expression is dependent on growth in high light. Tdy1 RNA is expressed in mature and immature leaves, developing ears and tassels and in seedling roots (Ma et al. 2009).
Other
tdy1 acts independently of Sxd1 (Ma et al. 2008).
tdy1 acts non-cell autonomously (Baker and Braun 2007).
tdy1 variegated leaf phenotype is independent of starch metabolism (Slewinski et al. 2008).
References
Baker RF, Braun DM. (2007) tie-dyed1 Functions non-cell autonomously to control carbohydrate accumulation in maize leaves. Plant Physiology 144:8867-879. PUBMED
Baker RF and Braun DM. (2008) Tie-dyed2 functions with tie-dyed1 to promote carbohydrate export from maize leaves. Plant Physiology 146:1085-1097. PUBMED
Braun DM, Ma Y, Inada N, Muszynski MG, Baker RF. (2006) tie-dyed1 regulates carbohydrate accumulation in maize leaves, Plant Physiology 142: 1511-1522. PUBMED
Golubovskaya IN, Hamant O, Timofejeva L, Wang CJ, Braun D, Meeley R, Cande WZ (2006) Alleles of afd1 dissect REC8 functions during meiotic prophase I, Journal of Cell Science 119: 3306-3315. PUBMED
Ma Y, Baker RF, Magallanes-Lundback M, DellaPenna D, Braun DM.(2008) Tie-dyed1 and sucrose export defective1 act independently to promote carbohydrate export from maize leaves. Planta 227:527-538. PUBMED
Ma Y, Slewinski TL, Baker RF, Braun DM (2009) Tie-dyed1 encodes a novel, phloem-expressed transmembrane protein that functions in carbohydrate partitioning. Plant Physiology 149:181-194. PUBMED
Slewinski TL, Ma Y, Baker RF, Huang M, Meeley R, Braun DM. (2008) Determining the role of Tie-dyed1 in starch metabolism: epistasis analysis with a maize ADP-glucose pyrophosphorylase mutant lacking leaf starch. J Heredity 99:61-666. PUBMED