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 (Ma1 – Ma6) that reduced photoperiod sensitivity and resulted in earlier flowering in long days. Prior studies identified the genes associated with Ma1 (PRR37), Ma3 (PHYB), Ma5 (PHYC) and Ma6 (GHD7) and characterized their role in the flowering time regulatory pathway. The current study focused on understanding the function and identity of Ma2. Ma2 delayed flowering in long days by selectively enhancing the expression of SbPRR37 (Ma1) and SbCO, genes that co-repress the expression of SbCN12, a source of florigen. Genetic analysis identified epistatic interactions between Ma2 and Ma4 and located QTL corresponding to Ma2 on SBI02 and Ma4 on SBI10. Positional cloning and whole genome sequencing identified a candidate gene for Ma2, Sobic.002G302700, which encodes a SET and MYND (SYMD) domain lysine methyltransferase. Nine sorghum genotypes previously identified as recessive for Ma2 contained the mutated version of Sobic.002G302700 present in 80M (ma2).

Genome‐wide mapping and prediction of plant architecture in a sorghum nested association mapping population

“…Overall, however, our observation that many sorghum QTL do not colocalize with homologs of canonical maize and rice vegetative development regulators (e.g., most QTL in Figure 3) suggests that much of the natural variation in vegetative morphology sorghum is due to genes not previously described in cereals. This finding is consistent with recent molecular cloning studies, which have revealed that while some classical sorghum genes are orthologs of canonical genes known from model crops (e.g., Tannin2 [Wu et al., 2019], Maturity6 [Murphy et al., 2014]), many others are novel genes (e.g., Dwarf1 [Yamaguchi et al., 2016], Maturity2 [Casto et al., 2019], Dry [Zhang et al., 2018]).…”

Epistatic interactions between PHOTOPERIOD1, CONSTANS1 and CONSTANS2 modulate the photoperiodic response in wheat

“…In most sorghum genotypes, SbCO1 operates as a flowering promoter in SD and as a flowering repressor in LD [ 39 ] and SbPRR37 as a flowering repressor in LD [ 14 , 40 ]. By contrast, the orthologous PPD1 gene in barley and wheat functions as a LD heading promoter [ 12 , 16 , 19 ] ( Fig 4 ).…”

Understanding Past, and Predicting Future, Niche Transitions based on Grass Flowering Time Variation

“…The balance of VRN2 and CO2 expression under long days determines exactly what complex will form; without cold the VRN2 NF-Y complex dominates to repress flowering, whereas with cold the CO2 NF-Y complex dominates to promote flowering. Currently PRR37/PPD-H1 is not known to be part of the NF-Y complex in wheat or barley, perhaps explaining why, in contrast to rice and sorghum (Koo et al, 2013;Casto et al, 2019), the protein product of this gene promotes flowering (Guedira et al 2016). Increased expression of PRR37/PPD-H1 is associated with daylength insensitivity to promote both longand short-day flowering in oat , whereas recessive mutations cause late flowering in wheat and barley under long days (Guedira et al 2016).…”