Physiological and molecular analysis of the interaction between aluminium toxicity and drought stress in common bean (Phaseolus vulgaris)

Journal of Experimental Botany, May 2012

Aluminium (Al) toxicity and drought are two major factors limiting common bean (Phaseolus vulgaris) production in the tropics. Short-term effects of Al toxicity and drought stress on root growth in acid, Al-toxic soil were studied, with special emphasis on Al–drought interaction in the root apex. Root elongation was inhibited by both Al and drought. Combined stresses resulted in a more severe inhibition of root elongation than either stress alone. This result was different from the alleviation of Al toxicity by osmotic stress (–0.60 MPa polyethylene glycol) in hydroponics. However, drought reduced the impact of Al on the root tip, as indicated by the reduction of Al-induced callose formation and MATE expression. Combined Al and drought stress enhanced up-regulation of ACCO expression and synthesis of zeatin riboside, reduced drought-enhanced abscisic acid (ABA) concentration, and expression of NCED involved in ABA biosynthesis and the transcription factors bZIP and MYB, thus affecting the regulation of ABA-dependent genes (SUS, PvLEA18, KS-DHN, and LTP) in root tips. The results provide circumstantial evidence that in soil, drought alleviates Al injury, but Al renders the root apex more drought-sensitive, particularly by impacting the gene regulatory network involved in ABA signal transduction and cross-talk with other phytohormones necessary for maintaining root growth under drought.

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Physiological and molecular analysis of the interaction between aluminium toxicity and drought stress in common bean (Phaseolus vulgaris)

Zhong-Bao Yang 2 Dejene Eticha 2 Alfonso Albacete 1 Idupulapati Madhusudana Rao 0 Thomas Roitsch 1 Walter Johannes Horst 2 0 International Center for Tropical Agriculture (CIAT) , AA 6713, Cali, Colombia 1 Institute of Plant Science, Karl-Franzens-Universita t Graz , Schubertstrasse 51, A-8010 Graz, Austria 2 Institute of Plant Nutrition, Leibniz Universita t Hannover , Herrenhaeuser Str. 2, D-30419 Hannover, Germany Aluminium (Al) toxicity and drought are two major factors limiting common bean (Phaseolus vulgaris) production in the tropics. Short-term effects of Al toxicity and drought stress on root growth in acid, Al-toxic soil were studied, with special emphasis on Al-drought interaction in the root apex. Root elongation was inhibited by both Al and drought. Combined stresses resulted in a more severe inhibition of root elongation than either stress alone. This result was different from the alleviation of Al toxicity by osmotic stress (-0.60 MPa polyethylene glycol) in hydroponics. However, drought reduced the impact of Al on the root tip, as indicated by the reduction of Al-induced callose formation and MATE expression. Combined Al and drought stress enhanced up-regulation of ACCO expression and synthesis of zeatin riboside, reduced drought-enhanced abscisic acid (ABA) concentration, and expression of NCED involved in ABA biosynthesis and the transcription factors bZIP and MYB, thus affecting the regulation of ABA-dependent genes (SUS, PvLEA18, KS-DHN, and LTP) in root tips. The results provide circumstantial evidence that in soil, drought alleviates Al injury, but Al renders the root apex more drought-sensitive, particularly by impacting the gene regulatory network involved in ABA signal transduction and cross-talk with other phytohormones necessary for maintaining root growth under drought. - Common bean (Phaseolus vlugaris L.) is the major food legume for human nutrition in the world, and a major source of calories and protein, particularly in many developing Latin American and African countries (Graham, 1978; Rao, 2001). Common bean production in the tropics is severely limited by two major abiotic stresses, drought and aluminium (Al) toxicity (Goldman et al., 1989; Ishitani et al., 2004). Generally, common bean has been regarded as an Al- and drought-sensitive crop (Rao, 2001; Beebe et al., 2008). In many regions of the developing world, drought and Al toxicity overlap (Wortmann et al., 1998; Thung and Rao, 1999; Beebe et al., 2011). Furthermore, on many acid soils, intermittent drought stress during the growing period could cause yield reduction of 3060% (CIAT, 1992; Wortmann et al., 1998). The root apex is the most Al-sensitive root zone (Horst et al., 1992; Delhaize and Ryan, 1995). In common bean, the transition zone (12 mm) and the elongation zone are targets of Al injury (Rangel et al., 2007). Excess Al will result in a rapid inhibition of root elongation and enhanced callose synthesis in the root tips; both are sensitive indicators of Al injury in roots (Delhaize and Ryan, 1995; Sta and Horst, 2009). Applying the pressure probe technique to 5 cm root tips of an Al-sensitive maize cultivar, Gunse et al. (1997) found that Al treatment decreased both the cellular and whole root hydraulic conductivities and cell wall extensibility. However, by application of Al only to the 1 cm root apex, Sivaguru et al. (2006) did not find any impairment of xylem water flow. Al resistance in common bean is related to lower Al accumulation in the root tips (Rangel et al., 2007). Lower Al accumulation and thus the detoxification of Al in the apoplast through root exudates, such as Al-activated exudation of citrate from root tips, play a key role in Al resistance in common bean (Miyasaka et al., 1991; Rangel et al., 2009, 2010; Horst et al., 2010). Eticha et al. (2010) showed that the Al-induced expression of a MATE (multidrug and toxin extrusion family protein) gene in root apices is a prerequisite for citrate exudation and Al resistance in common bean. In addition Al-induced inhibition of root elongation was positively correlated with the expression of an ACCO (1-aminocyclopropane-1-carboxylic acid oxidase) gene in the root apex (Eticha et al., 2010). The expression of MATE and ACCO has been used as a sensitive indicator of Al impact on the root apex in common bean (Yang et al., 2011). Drought strongly affects the root apex, leading to inhibition of root elongation (Sharp et al., 2004). The maintenance of root growth during water deficit is a prerequisite for water uptake from the subsoil (Sponchiado et al., 1989; Serraj and Sinclair, 2002). In maize, three mechanisms involved in primary root growth maintenance under water deficit have been proposed: osmotic adjustment; modification of cell wall (CW) extension properties; and the role of abscisic acid (ABA) accumulation (Sharp et al., 2004; Yamaguchi et al., 2010). To the authors knowledge the interaction of drought and Al at the level of the root apex (...truncated)


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Zhong-Bao Yang, Dejene Eticha, Alfonso Albacete, Idupulapati Madhusudana Rao, Thomas Roitsch, Walter Johannes Horst. Physiological and molecular analysis of the interaction between aluminium toxicity and drought stress in common bean (Phaseolus vulgaris), Journal of Experimental Botany, 2012, pp. 3109-3125, 63/8, DOI: 10.1093/jxb/ers038