Expression Profiling of Genes Underlying Drought Tolerance in Common Bean (Phaseolus vulgaris L.) and Influence of Arbuscular Mycorrhizal Fungi Symbiosis

In Brazil, common bean (Phaseolus vulgaris L.) productivity is severely affected by drought stress due to low technology cultivation systems. Therefore, identifying genes that regulate defense and adaptation mechanisms to the water deficit period is of primary importance. Arbuscular Mychorrizal Fungi (AMFs) might play an important role in stress tolerance by establishing mutualistic relationships vital for nutrient and water absorption, and regulating several genes as those for aquaporins. In a previous drought experiment we have selected 31 different ESTs derived from a SSH library contrasting the drought tolerant genotype BAT477 (tester) to the sensitive IAC-Carioca 80SH (driver). A series of qPCR assays considering those genotypes treated/untreated during different periods of time revealed induction of several drought responsive genes in roots associated to LEAs, cell wall structural proteins, transcription factors and also membrane transporters as aquaporins. Further experiment was performed contrasting BAT477 plants (roots and leaves) inoculated with AMFs (a mixture of Glomus clarum, Acaulosporea scrobiculata and Gigaspora rosea) to not inoculated, under drought/control with different harvesting periods. An in silico search provided eight different ESTs of the PIP group with orthologs to different legumes, including two new aquaporins not previously reported for P. vulgaris. Our qPCR results suggested the induction of MtAQP1 (up to 17 fold-change), MtPIP1,1 (4 fold-change), PvPIP1,2 (54 fold-change), PvPIP2,3 (10 fold-change), PvPIP2,3 (21 fold-change), PvPIP1,1 (10 fold-change). These genes seem to be strong candidates for breeding strategies aiming to drought tolerance and put AMFs as an important element to that concern.