IN INOCULANTS Nodulaid - 17th International Nitrogen Fixation ...

17 th International Congress on Nitrogen Fixation
Fremantle, Western Australia
27 November – 1 December 2011
Title Hui Zhu, Chao Wang, Liping Jin, Tao Chen, Longxiang Wang, Zhongming Zhang*
State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University
Authors Characterization of two splice variants of SIP1 and their functions during nodule
development in Lotus japonicas
Poster Board Number 4
Lotus japonicus SymRK and NIN genes are both required for the successful establishment of root nodule
symbiosis. Previously, we discovered that ARID family transcription factor SIP1 interacted with SymRK and
specifically bound to the AT-rich motif of NIN promoter (Zhu et al., 2008). However, the biological function of
SIP1 wasn‟t fully understood. Here, an isoform of SIP1 (called SIP1S in this work) was isolated, referred to as
SIP1L, which is produced by alternative splicing. SIP1L contains an ARID domain and an Hsp20 domain, while
SIP1S lacks the complete Hsp20 domain with 17 amino acids deletion. SIP1L presents a more abundant
expression than SIP1S and can‟t interact with SymRK in yeast, suggesting some characterizations of the two
splice variants are altered. However, SIP1L and SIP1S colocalize in nuclei in onion epidermal cells and form
homo- and heterocomplexes with itself and with each other, respectively, which is verified via yeast-two hybrid, in
vitro pull-down and BiFC assay in Nicotiana benthamiana. Overexpression of the less abundant SIP1S leads to
the increasing of the nodule number and RNA interference of SIP1 gene results in the significant impairment of
nodulation and the interrupted nodule formation during nodule primordial stage. Spatial expression by
SIP1p::GUS shows the centralized expression in the vascular tissue of developing nodule primordia. We propose
that SIP1L and SIP1S may form polymers and be involved in nodule development process. On the other hand,
we surprisedly find that suppressed SIP1 expression affects arbuscule formation, implicating the possible
function of SIP1 gene in arbuscular mycorrhizal symbiosis.
Zhu, H, Chen, T, Zhu, M, Fang, Q, Kang, H, Hong, Z, and Zhang, Z (2008). A novel ARID DNA-binding protein
interacts with SymRK and is expressed during early nodule development in Lotus japonicus. Plant Physiol
148:337-347.
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2011