|Chengbo, Zhou - University Of Georgia|
|Haibao, Tang - University Of Georgia|
|Prashant, Khadke - University Of Georgia|
|Sayan, Das - University Of Georgia|
|Yann-rong, Lin - National Taiwan University|
|Ge, Z. - University Of Nebraska|
|Clement, T. - University Of Nebraska|
|Upadhyaya, H.d. - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India|
|Hash, C.t. - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India|
|Patterson, Andrew - International Crops Research Institute For Semi-Arid Tropics (ICRISAT) - India|
Submitted to: Molecular Biology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2016
Publication Date: 6/22/2016
Citation: Cuevas, H.E., Chengbo, Z., Haibao, T., Prashant, K., Sayan, D., Yann-Rong, L., Ge, Z., Clement, T., Upadhyaya, H., Hash, C., Patterson, A.H. 2016. The evolution of photoperiod-sensitive flowering in sorghum, a genomic model for panicoid grasses. Molecular Biology and Evolution. 33:2417-2428. doi:10.1093/molbev/msw120.
Interpretive Summary: Flowering time in sorghum (Sorghum bicolor) is determined by day length. The majority of exotic sorghum accessions flower under short day length (e.g. less than 12 hr), while temperate commercial varieties are photoperiod insensitive (‘day-neutral’) and flowering is dependent on accumulation of heat units. Herein, we identify Ma1, the gene responsible for the short-day flowering of most tropical sorghums by genotype and phenotype 96 near isogenic lines and 384 diverse sorghum accessions. The gene was located in a low recombination region of chromosome six which favor its survival and further selection over millions of years. The SNP markers developed in our study can be used to as an important tool for marker assisted selection to convert photoperiod sensitive cultivars into temperate adapted sorghum germplasm.
Technical Abstract: Water loss from a plant is a direct consequence of photosynthesis, and diverse plants share maximal sensitivity to water deficit at flowering. Flowering under short daylength (e.g. less than 12 hr) coordinates fecundity and seed development with favorable rainfall, temperature, and solar radiation in the semi-arid tropical habitats to which many cereals are native. To adapt tropical plants to temperate agriculture, photoperiod insensitive (‘day-neutral’) mutants have been selected to flower based on accumulation of heat units in order to use the long days of the temperate summer. Here we identify Ma1, the gene responsible for the short-day flowering of most tropical sorghums. Temperate adaptation of sorghum at this locus by scientific breeding was paralleled, or more probably preceded, by independent mutation in S. halepense, a tropical native now naturalized and/or invasive in temperate regions of six continents. The origin of Ma1 as a single-gene duplication ~40 million years ago adds to evidence from another major innovation, C4 photosynthesis, that adaptation to fluctuating environments may favor continuously-produced single-gene duplicates over products of episodic genome duplications. The survival of Ma1 for long enough to evolve important function may have been favored by its location in the most recombination recalcitrant region of the sorghum genome, where neutral or slightly-deleterious mutations tend to be longer-lived. The conditions that favored survival of Ma1 may also have nurtured formation of a ‘co-adapted gene complex’ implicated in plant stature and other aspects of growth and development. The identification of Ma1 gene improves our understanding of flowering time in sorghum, and facilitates the use of exotic germplasm in sorghum breeding programs.