The Lotus japonicus Genome

lines are ordered through Legume Base (http://
http://www.legumebase.brc.miyazaki-u.ac.jp/lore1Browse
Action.do), whereas the Danish lines are ordered
from the CARB Web site (http://carb.au.dk/lore1/).
As of January 2014, more than 1,800LORE1lines
had been dispatched to 19 different countries.

20.8 Future Perspectives

From studying theLORE1retrotransposon, we
now know that epigenetic activation of TEs can be
induced by tissue culture and that their active
states can be inherited by the regenerated plants.
However, when the TEs lack activity in cultured
cells, the activation cannot be detected as trans-
positions in thefirst generation of regenerated
plants (R0), since germinal transpositions will
only be detectable from R1 and later generations.
These activation events may occur in tissue cul-
ture experiments for any plant species and would
usually be overlooked. Looking at the segregation
of mutant phenotypes derived from a regenerated
plant population, while keeping such a scenario in
mind, could lead to the identification of endoge-
nous TEs, which can be activated by tissue

culture. The generation of theLORE1mutant

resource has demonstrated the cost-effectiveness

of using endogenous TEs for mutagenesis. A lit-

erature search for evidence of recent transposi-

tions or empirical confirmation of transposition

activity revealed a number of endogenous legume

TEs that could possibly be used for large-scale

mutagenesis (Table20.2). Combined use of model

and crop legume mutant collections will strongly

facilitate legume molecular biological studies and

will contribute to solving agronomical and envi-

ronmental issues worldwide.

References

Alonso JM et al (2003) Genome-wide insertional mutagen-

esisofArabidopsisthaliana.Science301(5633):653– 657

Bolon YT, Haun WJ, Xu WW, Grant D, Stacey MG,

Nelson RT, Gerhardt DJ, Jeddeloh JA, Stacey G,

Muehlbauer GJ, Orf JH, Naeve SL, Stupar RM, Vance

CP (2011) Phenotypic and genomic analyses of a fast

neutron mutant population resource in soybean. Plant

Physiol 156:240– 253

Cui Y, Barampuram S, Stacey MG, Hancock CN, Findley

S, Mathieu M, Zhang Z, Parrott WA, Stacey G (2013)

Tnt1 retrotransposon mutagenesis: a tool for soybean

functional genomics. Plant Physiol 161:36– 47

Table 20.2 Endogenous TEs in legumes with evidence of recent activity

Host Name of

TE

class

I/II

Evidence of

activity

Activity identified in/as References

L. japonicus LORE1 I Transpositions Regenerated plants from

cultured cells

Fukai et al. ( 2010 ),

Madsen et al. ( 2005 )

LORE2 I Transpositions Regenerated plants from

cultured cells

Fukai et al. ( 2008 )

M. truncatula MERE1 I

Transpositions Cultured cells Rakocevic et al. ( 2009 )

Soybean Tgm II Excisions,

New

mutations

Somatic and germ cells Xu et al. ( 2010 ), Zabala

and Vodkin ( 2005 ,

2008 )

SORE- 1 I Recent

transpositions

Spontaneous mutations during

breeding

Kanazawa et al. ( 2009 ),

Liu et al. ( 2008 )

Peanut AhMITE1 I Excision Spontaneous mutation,

excision induced by chemical

mutagen, Gamma ray, Tissue

culture

Gowda et al. ( 2010 ,

2011 ), Patel et al.

( 2004 ), Shirasawa et al.

( 2012 )

20 Forward and Reverse Genetics... 225