Loss of an MDR Transporter in Compact Stalks of Maize br2 and Sorghum dw3 Mutants

Abstract

Agriculturally advantageous reduction in plant height is usually achieved by blocking the action or production of gibberellins. Here, we describe a different dwarfing mechanism found in maize brachytic2 (br2) mutants characterized by compact lower stalk internodes. The height reduction in these plants results from the loss of a P-glycoprotein that modulates polar auxin transport in the maize stalk. The sorghum ortholog of br2 is dwarf3 (dw3), an unstable mutant of long-standing commercial interest and concern. A direct duplication within the dw3 gene is responsible for its mutant nature and also for its instability, because it facilitates unequal crossing-over at the locus.

3D sorghum reconstructions from depth images identify QTL regulating shoot architecture

“…Comparison of QTL intervals identified using image-based phenotyping with previously reported QTL intervals in the literature Most QTL intervals identified with the platform overlapped with QTLs or causal genes reported previously for related phenotypes (Hart et al, 2001;Feltus et al, 2006;Mace and Jordan, 2011;Morris et al, 2013;Higgins et al, 2014). Dw3 was cloned previously (Multani et al, 2003). For imagebased QTL intervals, the LOD-2 interval and peak coordinate for the phenotype with the maximum MLOD are reported, and the phenotype name is indicated by an asterisk; maximum MLOD coordinates are not applicable to intervals from the literature, indicated by a dash.…”

“…A significant association between Dw3 and shoot cylinder height is not observed until the second time point (34 DAP), while different alleles of Dw3 introduce significant variability in leaf angle by the earliest time point (27 DAP). This is likely because Dw3 impacts height by impacting stem elongation and the stem has not yet begun to elongate substantially by the earliest time point; as such, the nonfunctional dw3 allele caused smaller leaf angles prior to any significant effect on stem elongation (Multani et al, 2003;Truong et al, 2015). Similar to Dw3, the effects of Dw2, a sorghum dwarfing gene on chromosome 6 near 42 Mb (but not yet cloned), are significantly associated with shoot cylinder height after the first time point (34, 39, and 44 DAP); unlike Dw3, Dw2 is not significantly associated with any other pleiotropic effects on leaf morphology.…”

“…The parents of the imaged RIL population, BTx623 and IS3620C, are fixed for nonfunctional and functional forms, respectively, of the Dw3 gene, which encodes an auxin efflux protein that has pleiotropic effects on stem elongation and additional architecture traits like leaf angle (Multani et al, 2003;Truong et al, 2015). A significant association between Dw3 and shoot cylinder height is not observed until the second time point (34 DAP), while different alleles of Dw3 introduce significant variability in leaf angle by the earliest time point (27 DAP).…”

Association mapping for phenology and plant architecture in maize shows higher power for developmental traits compared with growth influenced traits

“…Only domestication genes, flowering time and plant height have been fully documented. Most of major developmental genes that have been cloned are fixed in elite germplasm, such as the Tb1 allele that suppresses tillering (Doebley et al, 1997), the Tga allele that confers naked grains (Wang et al, 2005) and the Br2 allele that reduces plant height (Multani et al, 2003). However, substantial variation remains to be explained and exploited for most traits.…”

Isolation, Characterization, and Pericycle-Specific Transcriptome Analyses of the Novel Maize Lateral and Seminal Root Initiation Mutant rum1

“…Several genes involved in auxin transport, including the postulated efflux carriers of the pin family (Gälweiler et al, 1998;Mü ller et al, 1998;Friml et al, 2002aFriml et al, , 2002b, the auxin importer aux1 (Marchant et al, 1999), and the postulated efflux carriers pgp1, pgp2, and pgp19 (Noh et al, 2001), have been cloned recently in Arabidopsis. The maize ortholog of pgp1 is not expressed in roots (Multani et al, 2003).…”