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JXB Advance Access originally published online on December 3, 2008
Journal of Experimental Botany 2009 60(2):533-546; doi:10.1093/jxb/ern296
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© 2008 The Author(s).
This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/2.0/uk/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. This paper is available online free of all access charges (see http://jxb.oxfordjournals.org/open_access.html for further details)

RESEARCH PAPER

The ER luminal binding protein (BiP) mediates an increase in drought tolerance in soybean and delays drought-induced leaf senescence in soybean and tobacco

Maria Anete S. Valente1, Jerusa A. Q. A. Faria1, Juliana R. L. Soares-Ramos1, Pedro A. B. Reis1, Guilherme L. Pinheiro1, Newton D. Piovesan1, Angélica T. Morais2, Carlos C. Menezes3, Marco A. O. Cano4, Luciano G. Fietto1, Marcelo E. Loureiro4, Francisco J. L. Aragão2 and Elizabeth P. B. Fontes1,*

1Departamento de Bioquímica e Biologia Molecular, BIOAGRO, Universidade Federal de Viçosa, Avenida PH Rolfs s/n, 36571.000 Viçosa, MG, Brazil
2Embrapa Recursos Genéticos e Biotecnologia, PqEB W5 Norte, 70770-900, Brasília, DF, Brazil
3Universidade de Rio Verde, Fazenda Fontes do Saber, 75901-970, Rio Verde, GO, Brazil
4Departamento de Biologia Vegetal, Universidade Federal de Viçosa, 36571.000, Viçosa, MG, Brazil

* To whom correspondence should be addressed: E-mail: bbfontes{at}ufv.br

The ER-resident molecular chaperone BiP (binding protein) was overexpressed in soybean. When plants growing in soil were exposed to drought (by reducing or completely withholding watering) the wild-type lines showed a large decrease in leaf water potential and leaf wilting, but the leaves in the transgenic lines did not wilt and exhibited only a small decrease in water potential. During exposure to drought the stomata of the transgenic lines did not close as much as in the wild type, and the rates of photosynthesis and transpiration became less inhibited than in the wild type. These parameters of drought resistance in the BiP overexpressing lines were not associated with a higher level of the osmolytes proline, sucrose, and glucose. It was also not associated with the typical drought-induced increase in root dry weight. Rather, at the end of the drought period, the BiP overexpressing lines had a lower level of the osmolytes and root weight than the wild type. The mRNA abundance of several typical drought-induced genes [NAC2, a seed maturation protein (SMP), a glutathione-S-transferase (GST), antiquitin, and protein disulphide isomerase 3 (PDI-3)] increased in the drought-stressed wild-type plants. Compared with the wild type, the increase in mRNA abundance of these genes was less (in some genes much less) in the BiP overexpressing lines that were exposed to drought. The effect of drought on leaf senescence was investigated in soybean and tobacco. It had previously been reported that tobacco BiP overexpression or repression reduced or accentuated the effects of drought. BiP overexpressing tobacco and soybean showed delayed leaf senescence during drought. BiP antisense tobacco plants, conversely, showed advanced leaf senescence. It is concluded that BiP overexpression confers resistance to drought, through an as yet unknown mechanism that is related to ER functioning. The delay in leaf senescence by BiP overexpression might relate to the absence of the response to drought.

Key words: Binding protein, BiP, drought tolerance, environmental stresses, leaf senescence, soybean

Received 17 September 2008; Revised 28 October 2008 Accepted 29 October 2008


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