OsLG1 regulates a closed panicle trait in domesticated rice

Abstract

Reduction in seed shattering was an important phenotypic change during cereal domestication. Here we show that a simple morphological change in rice panicle shape, controlled by the SPR3 locus, has a large impact on seed-shedding and pollinating behaviors. In the wild genetic background of rice, we found that plants with a cultivated-like type of closed panicle had significantly reduced seed shedding through seed retention. In addition, the long awns in closed panicles disturbed the free exposure of anthers and stigmas on the flowering spikelets, resulting in a significant reduction of the outcrossing rate. We localized the SPR3 locus to a 9.3-kb genomic region, and our complementation tests suggest that this region regulates the liguleless gene (OsLG1). Sequencing analysis identified reduced nucleotide diversity and a selective sweep at the SPR3 locus in cultivated rice. Our results suggest that a closed panicle was a selected trait during rice domestication.

Regulatory modules controlling maize inflorescence architecture

“…One hypothesis is that lg1 also promotes BM identity by regulating cell division at the adaxial surface of indeterminate SPMs. A recent report in rice showed direct association of a key panicle architecture trait with regulation of OsLG1 (Ishii et al 2013). Since RA1 is not present in rice, multiple modes of lg1 regulation may have been co-opted for inflorescence development during evolution, and possibly for tissue-specific regulation, e.g., through lg1 association with leaf angle in maize Tian et al 2011).…”

“…Central to this variation are unique branching patterns that contribute directly to traits such as grain yield, harvestability, and hybrid seed production (Kellogg 2007;Huang et al 2009;Sreenivasulu and Schnurbusch 2012;Ishii et al 2013). Among grasses, inflorescence architecture is diverse, yet characterized by a unique morphology, where flowers are borne on specialized short branches called spikelets (Kellogg 2007;Thompson and Hake 2009).…”

Gene regulatory interactions at lateral organ boundaries in maize

“…A QTL for rice domestication mapped to a region 10 kb upstream of lg1. Expression of lg1 was increased in undomesticated varieties that had a larger branch angle than domesticated varieties (Ishii et al, 2013;Zhu et al, 2013). In maize, lg2 mutants have few, upright tassel branches (Walsh and Freeling, 1999).…”

“…Quantitative trait mapping identified a region upstream of lg1 as a QTL for domestication in rice (Ishii et al, 2013;Zhu et al, 2013). In maize, comparisons of ear and tassel expression showed that lg1 is normally excluded from ear primordia but is expressed in the highly branched ear of a ramosa1 mutant (Eveland et al, 2013).…”

Identification of Quantitative Trait Loci Controlling Floral Morphology of Rice Using a Backcross Population between Common Cultivated Rice, <i>Oryza sativa</i> and Asian Wild Rice, <i>O. rufipogon</i>

“…This difference in pollination behaviour was likely mediated by the selection of the naturally occurring mutations during rice domestication. An interesting change affecting pollination behaviour in rice is a closed panicle trait, which was selected in the early stages of domestication to increase seed harvesting efficiency [9]. In addition to increasing yield, the closed panicle trait was also shown to increase self-pollination, as longer awns on the top of seeds located at the lower part of the panicle block free exposure of the anther at the upper part of panicle.…”