A gain-of-function Bushy dwarf tiller 1 mutation in rice microRNA gene miR156d caused by insertion of the DNA transposon nDart1

Abstract

A non-autonomous DNA transposon in rice, nDart1, is actively transposed in the presence of an autonomous element, aDart1, under natural conditions. The nDart1-promoted gene tagging line was developed using the endogenous nDart1/aDart1 system to generate various rice mutants effectively. While the dominant mutants were occasionally isolated from the tagging line, it was unclear what causes dominant mutations. A semidominant mutant, Bushy dwarf tiller1 (Bdt1), which has the valuable agronomic traits of multiple tillering and dwarfism, was obtained from the tagging line. Bdt1 mutant carried a newly inserted nDart1 at 38-bp upstream of transcription initiation site of a non-protein-coding gene, miR156d. This insertion caused an upstream shift of the miR156d transcription initiation site and, consequently, increased the functional transcripts producing mature microRNAs. These results indicate that the total amount of miR156d is controlled not only by transcript quantity but also by transcript quality. Furthermore, transgenic lines introduced an miR156d fragment that flanked the nDart1 sequence at the 5′ region, suggesting that insertion of nDart1 in the gene promoter region enhances gene expression as a cis-element. This study demonstrates the ability of nDart1 to produce gain-of-function mutants as well as further insights into the function of transposable elements in genome evolution.

Modulation of plant architecture by the miR156f–OsSPL7–OsGH3.8 pathway in rice

“…In this study, we showed that miR156f is a positive regulator of tiller number and a negative regulator of plant height. Consistent with its conserved function, several of the 12 miR156 genes in rice have been reported as influencing tiller number and plant height ( Xie et al , 2006 ; Chen et al , 2015 ; Hayashi-Tsugane et al , 2015 ; Wang et al , 2015 ). There are also 18 miR156 target SPL genes in rice, and the functions of some of these have already been determined ( Jiao et al , 2010 ; Miura et al , 2010 ; Springer, 2010 ).…”

An Acyl-CoA N-Acyltransferase Regulates Meristem Phase Change and Plant Architecture in Barley

“…Overexpression of miR156 in the dominant Cg1 mutant in maize caused a delay in juvenile-to-adult phase change, an increase in the number of leaves and tillers, a delay in flowering, and development of small ears with large bracts (Chuck et al, 2007). Similarly, a semidominant rice mutant, Bushy dwarf tiller1 (Bdt1), with increased expression of miR156, displayed high tillering and small panicles with overgrown bracts and leaf-like structures (Hayashi-Tsugane et al, 2015). In addition, overexpression of miR172b in rice delayed the transition from spikelet meristem to floral meristem.…”

Hybrid incompatibilities in interspecific crosses between tetraploid wheat and its wild diploid relative Aegilops umbellulata

“…tauschii. Especially, miR156 overexpression induces morphological changes, including dwarfism, increased tiller number and late flowering through down-regulation of SPLs in maize, switchgrass and rice (Chuck et al 2007;Fu et al 2012;Hayashi-Tsugane et al 2015). Phenotypic characters of transformants overexpressing miR156 closely resembled grass-clump dwarfism of Ldn/Ae.…”