Transcriptomic analysis reveals differential gene expression in response to aluminium in common bean (Phaseolus vulgaris) genotypes.
OBJECTIVE
Aluminium (Al) resistance in common bean is known to be due to exudation of citrate from the root after a lag phase, indicating the induction of gene transcription and protein synthesis. The aims of this study were to identify Al-induced differentially expressed genes and to analyse the expression of candidate genes conferring Al resistance in bean.


METHODS
The suppression subtractive hybridization (SSH) method was used to identify differentially expressed genes in an Al-resistant bean genotype ('Quimbaya') during the induction period. Using quantitative real-time PCR the expression patterns of selected genes were compared between an Al-resistant and an Al-sensitive genotype ('VAX 1') treated with Al for up to 24 h.


RESULTS
Short-term Al treatment resulted in up-regulation of stress-induced genes and down-regulation of genes involved in metabolism. However, the expressions of genes encoding enzymes involved in citrate metabolism were not significantly affected by Al. Al treatment dramatically increased the expression of common bean expressed sequence tags belonging to the citrate transporter gene family MATE (multidrug and toxin extrusion family protein) in both the Al-resistant and -sensitive genotype in close agreement with Al-induced citrate exudation.


CONCLUSIONS
The expression of a citrate transporter MATE gene is crucial for citrate exudation in common bean. However, although the expression of the citrate transporter is a prerequisite for citrate exudation, genotypic Al resistance in common bean particularly depends on the capacity to sustain the synthesis of citrate for maintaining the cytosolic citrate pool that enables exudation.
Institute of Plant Nutrition, Leibniz University Hannover, Herrenhaeuser Str. 2, 30419 Hannover, Germany.
Dejene
D
Eticha
Marc
M
Zahn
Melanie
M
Bremer
Zhongbao
Z
Yang
Andrés F
AF
Rangel
Idupulapati M
IM
Rao
Walter J
WJ
Horst
D000535:Aluminum / Q000633:toxicity*; D002352:Carrier Proteins / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects* / Q000235:genetics; D005838:Genotype; D027805:Phaseolus / Q000187:drug effects* / Q000235:genetics*; D010940:Plant Proteins / Q000235:genetics; D016133:Polymerase Chain Reaction
D002352:Carrier Proteins; D010940:Plant Proteins; C020723:citrate-binding transport protein; D000535:Aluminum