Interaction between rhizobia and robinia pseudoacacia and environment

Hongyan Chen, Minxia Chou, Gehong Wei*

College of Life Sciences, State Key Laboratory of Crop Stress Biology in Arid Areas, Northwest A & F University, Yangling, Shaanxi 712100, China.
*Corresponding Author: Tel: (+8629) 87091175; Fax: (+8629) 87091175; E-mail: weigehong@yahoo.com.cn

Abstract
For legumes, many nodulin genes, which are upregulated during different stages of nodulation, have been identified, but for woody legume tree black locust (Robinia pseudoacacia), none of nodulin genes have been reported. We applied a suppressive subtractive hybridization (SSH) approach to identify nodule-enhanced genes using two mRNA populations of infected and uninfected control roots of Robinia pseudoacacia and constructed a subtractive cDNA library, which contained ~600 colnes. 191 cDNA clones picked up by differential screening out of 371 clones were sequenced and 118 unigenes were identified, putative functions of the translational products can be classified into 13 categories. By reverse transcription–polymerase chain reaction (RT-PCR), 21 upregulated genes encoding potential regulatory protein were selected, including nine putative transcription genes and eight genes about post-translational modification and four membrane protein genes. The expression patterns of these genes were further analyzed by real-time RT-PCR at different stages during nodule development. Among these genes, open reading frames of eight genes were successfully determined by rapid amplification of cDNA ends (RACE). Based on the results, for the first time, these data provide a global resource for transcriptional events important for nodulation in Robinia pseudoacacia and suggested that the symbiosis is controlled by coordinated gene expression. In addition, the possible roles of some genes involve in the rhizobia infection and nodule development and nitrogen fixation were discussed.

Key Words: woody legume tree; nodulin gene; SSH; Black Locust