Childs K L, Miller F R, Cordonnier-Pratt M M, Pratt L H, Morgan P W, Mullet J E
Department of Biochemistry and Biophysics, Texas A&M University, College Station 77843-2128, USA.
Plant Physiol. 1997 Feb;113(2):611-9. doi: 10.1104/pp.113.2.611.
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.
Ma3基因是调控高粱（Sorghum bicolor [L.] Moench）开花光周期敏感性的六个基因之一。该基因的ma3R突变导致的表型类似于已知缺乏phytochrome B的植物，且ma3高粱缺乏一种在光照生长的植物中占主导且存在于非ma3植物中的123-kD phytochrome。构建了一个Ma3和ma3分离的群体，并用于鉴定与Ma3连锁的两个随机扩增多态性DNA标记。这两个标记被克隆，并在重组自交群体中作为限制性片段长度多态性进行定位。从绿色高粱叶片制备的cDNA文库中克隆并测序了PHYA和PHYC的cDNA克隆。使用基因组步移技术，从ma3高粱的基因组DNA中确定了7941-bp的PHYB部分序列。PHYA、PHYB和PHYC均定位于同一连锁群。与Ma3连锁的标记与PHYB的定位距离PHYA和PHYC超过121厘摩。在ma3高粱的PHYB序列中发现了一个导致提前终止密码子的移码突变。因此，我们得出结论，高粱中的Ma3位点是一个编码123-kD phytochrome的PHYB基因。
