Maturity2, a novel regulator of flowering time in Sorghum bicolor, increases expression of SbPRR37 and SbCO in long days delaying flowering

Abstract

Sorghum bicolor is a drought-resilient facultative short-day C4 grass that is grown for grain, forage, and biomass. Adaptation of sorghum for grain production in temperate regions resulted in the selection of mutations in Maturity loci (Ma 1 –Ma 6 ) that reduced photoperiod sensitivity and resulted in earlier flowering in long days. Prior studies identified the genes associated with Ma 1 (PRR37), Ma 3 (PHYB), Ma 5 (PHYC) and Ma 6 (GHD7) and characterized their role in the flowering time regulatory pathway. The current study focused on understanding the function and identity of Ma 2 . Ma 2 delayed flowering in long days by selectively enhancing the expression of SbPRR37 (Ma 1 ) and SbCO, genes that co-repress the expression of SbCN12, a source of florigen. Genetic analysis identified epistatic interactions between Ma 2 and Ma 4 and located QTL corresponding to Ma 2 on SBI02 and Ma 4 on SBI10. Positional cloning and whole genome sequencing identified a candidate gene for Ma 2 , Sobic.002G302700, which encodes a SET and MYND (SYMD) domain lysine methyltransferase. Eight sorghum genotypes previously identified as recessive for Ma 2 contained the mutated version of Sobic.002G302700 present in 80M (ma 2 ) and one additional putative recessive ma 2 allele was identified in diverse sorghum accessions.