MERE1, a Low-Copy-Number Copia-Type Retroelement in Medicago truncatula Active during Tissue Culture    

Abstract

We have identified an active Medicago truncatula copia-like retroelement called Medicago RetroElement1-1 (MERE1-1) as an insertion in the symbiotic NSP2 gene. MERE1-1 belongs to a low-copy-number family in the sequenced Medicago genome. These copies are highly related, but only three of them have a complete coding region and polymorphism exists between the long terminal repeats of these different copies. This retroelement family is present in all M. truncatula ecotypes tested but also in other legume species like Lotus japonicus. It is active only during tissue culture in both R108 and Jemalong Medicago accessions and inserts preferentially in genes.

Medicago truncatula DNF2 is a PI‐PLC‐XD‐containing protein required for bacteroid persistence and prevention of nodule early senescence and defense‐like reactions

“…The Tnt1 insertion mutant lines were generated at the Noble Foundation (Tadege et al, 2008). The MERE1 insertion mutant line MS240 corresponds to a somaclonal variant obtained by regeneration of a T-DNA-tagged Medicago line (Scholte et al, 2002;Brocard et al, 2006;Rakocevic et al, 2009). For expression studies using the b-glucuronidase reporter gene, transgenic plants expressing a DNF2 promoter::gus fusion (pMB132 construct, see later) were generated by Agrobacterium tumefaciens strain EHA105 transformation of M. truncatula R108, as described in Cosson et al (2006).…”

Mutagenesis and Beyond! Tools for Understanding Legume Biology

“…LORE1 and LORE2 in L. japonicus are Ty3/ gypsy-like retroelements (Fukai et al, 2008) that have similar potential for isolating knockout mutants in this model to the use of Tnt1 in M. truncatula. Likewise, MERE1 in M. truncatula is a copia-like element found to transpose during tissue culture at a reduced frequency when compared to the heterologous Tnt1 (Rakocevic et al, 2009).…”

TheTrans-Acting Short Interfering RNA3 Pathway and NO APICAL MERISTEM Antagonistically Regulate Leaf Margin Development and Lateral Organ Separation, as Revealed by Analysis of anargonaute7/lobed leaflet1Mutant inMedicago truncatula

“…Further analysis showed that a Tnt1 retrotransposon was inserted in exons of LOL1 in lol1-1, lol1-2, and lol1-3. However, lol1-4 carried a native retrotransposon, Medicago RetroElement1 (Rakocevic et al, 2009) (Figure 3A). The expression of LOL1 was interrupted in all four lol1 alleles ( Figure 3C).…”