Brachypodium distachyon T-DNA insertion lines: a model pathosystem to study nonhost resistance to wheat stripe rust

Abstract

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (PST), is one of the most destructive diseases and can cause severe yield losses in many regions of the world. Because of the large size and complexity of wheat genome, it is difficult to study the molecular mechanism of interaction between wheat and PST. Brachypodium distachyon has become a model system for temperate grasses’ functional genomics research. The phenotypic evaluation showed that the response of Brachypodium distachyon to PST was nonhost resistance (NHR), which allowed us to present this plant-pathogen system as a model to explore the immune response and the molecular mechanism underlying wheat and PST. Here we reported the generation of about 7,000 T-DNA insertion lines based on a highly efficient Agrobacterium-mediated transformation system. Hundreds of mutants either more susceptible or more resistant to PST than that of the wild type Bd21 were obtained. The three putative target genes, Bradi5g17540, BdMYB102 and Bradi5g11590, of three T-DNA insertion mutants could be involved in NHR of Brachypodium distachyon to wheat stripe rust. The systemic pathologic study of this T-DNA mutants would broaden our knowledge of NHR, and assist in breeding wheat cultivars with durable resistance.

Insertional mutagenesis of Brachypodium distachyon using the Tnt1 retrotransposable element

“…Although there are over 25 000 T-DNA lines, only 31% of the genes (about 8000) were reportedly tagged (Hsia et al, 2017). Additionally, a separate T-DNA collection of 7000 B. distachyon lines was developed to identify mutants that compromise nonhost resistance against wheat stripe rust pathogen (An et al, 2016). Here we report that the tobacco retrotransposon Tnt1 can transpose in B. distachyon during somatic embryogenesis and can be used as a mutagen to achieve saturation or near-saturation mutagenesis.…”

“…Insertion mutagenesis based on T-DNA is also popularly used in plants such as Arabidopsis (Alonso et al, 2003), rice (Jeon et al, 2000) and, more recently, B. distachyon (An et al, 2016;Hsia et al, 2017). A total of 21 165 B. distachyon T-DNA lines were sequenced as part of the Joint Genome Institute sequencing efforts, bringing the total of unique insertion sites to 26 112 (Hsia et al, 2017).…”

“…A T-DNA tagging collection of B. distachyon with a limited number of lines (about 23 000) has been generated (Thole et al, 2012). Similarly, in a different study, about 7000 T-DNA lines of B. distachyon were generated to study their effective role as a non-host to wheat stripe rust pathogen (An et al, 2016). However, the number of lines required to achieve saturation or near-saturation mutagenesis using T-DNA is considerably higher than using Tnt1.…”

Characterization and Genetic Analysis of Rice Mutant crr1 Exhibiting Compromised Non-host Resistance to Puccinia striiformis f. sp. tritici (Pst)

“…This region contains about 40 annotated genes, and there is no previously annotated host or non-host resistance gene in the interval. Recently, three genes involved in Brachypodium NHR to Pst were identified by flanking sequence isolation from mutant (An et al, 2016). Among them, Bradi5g17540 encodes a BAP28 domain containing protein, Bradi5g17540 encodes a MYB transcription factor and Bradi5g11590 encodes a lipoxygenase.…”

Optimizing callus induction and proliferation for Agrobacterium-mediated transformation of Brachypodium distachyon

“…There are different ways for selection and screening of transgenic calli by using reporter genes like uidA or gfp (An et al 2016). Also, both HPT (hygromicin B resistance) and BAR genes (Basta®/ Bialaphos resistance) can be used as selectable markers (Thole and Vain 2012;Steinwand et al 2013;Bragg et al 2012Bragg et al , 2015.…”