title: The sorghum photoperiod sensitivity gene, Ma3, encodes a phytochrome B.
abstract: The Ma3 gene is one of six genes that regulate the photoperiodic sensitivity of flowering in sorghum (Sorghum bicolor [L.] Moench). The ma3R mutation of this gene causes a phenotype that is similar to plants that are known to lack phytochrome B, and ma3 sorghum lacks a 123-KD phytochrome that predominates in light-grown plants and that is present in non-ma3 plants. A population segregating for Ma3 and ma3 was created and used to identify two randomly amplified polymorphic DNA markers linked to Ma3. These two markers were cloned and mapped in a recombinant inbred population as restriction fragment length polymorphisms. cDNA clones of PHYA and PHYC were cloned and sequenced from a cDNA library prepared from green sorghum leaves. Using a genome-walking technique, a 7941-bp partial sequence of PHYB, was determined from genomic DNA from ma3 sorghum. PHYA, PHYB, and PHYC all mapped to the same linkage group. The Ma3-linked markers mapped with PHYB more than 121 centimorgans from PHYA and PHYC. A frameshift mutation resulting in a premature stop codon was found in the PHYB sequence from ma3 sorghum. Therefore, we conclude that the Ma3 locus in sorghum is a PHYB gene that encodes a 123-kD phytochrome.
authors.affiliation: Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843-2128, USA.
authors.forename: K L
authors.initials: KL
authors.lastname: Childs
authors.forename: F R
authors.initials: FR
authors.lastname: Miller
authors.forename: M M
authors.initials: MM
authors.lastname: Cordonnier-Pratt
authors.forename: L H
authors.initials: LH
authors.lastname: Pratt
authors.forename: P W
authors.initials: PW
authors.lastname: Morgan
authors.forename: J E
authors.initials: JE
authors.lastname: Mullet
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002874:Chromosome Mapping; D003001:Cloning, Molecular; D003624:Darkness; D015870:Gene Expression; D017343:Genes, Plant; D005819:Genetic Markers; D008027:Light; D008969:Molecular Sequence Data; D009154:Mutation; D017440:Photoperiod; D010786:Photoreceptor Cells; D010834:Phytochrome / Q000235:genetics*; D051939:Phytochrome B; D006109:Poaceae / Q000235:genetics* / Q000528:radiation effects; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D014157:Transcription Factors
chemical_list: D005819:Genetic Markers; D014157:Transcription Factors; D010834:Phytochrome; D051939:Phytochrome B