Alternative oxidase regulation in roots of Vigna unguiculata cultivars differing in drought/salt tolerante

COSTA, J.H; JOLIVET, Y.; HASENFRATZ-SAUDER, M-P.; ORELLANO, E.G.; SILVA LIMA, M. DA G.; DIZENGREMEL, P.; FERNANDES DE MELO, D.

JOURNAL OF PLANT PHYSIOLOGY

Urban & Fisher, Elsevier Group

Lugar: Heidelberg; Año: 2007 vol. 164 p. 718 - 727

0176-1617

The alternative oxidase (Aox) was studied at different levels (transcript, protein and capacity) in response to an osmotic shock applied to roots of cowpea (Vigna unguiculata). Two cultivars of V. unguiculata were used, Vita 3 and Vita 5, tolerant and sensitive to drought/saline stress respectively. The seedlings (17-day-old) were grown in hydroponic conditions and submitted to NaCl (100 and 200 mM) or 200.67 g L1 PEG 6000 (iso-osmotic condition to 100mMNaCl). The VuAox1 and VuAox2a mRNA were not detected in either cultivar under all tested conditions while the VuAox2b gene was differently expressed. In the tolerant cultivar (Vita 3), the expression of VuAox2b gene was stimulated by an osmotic stress induced by PEG which was associated with a higher amount and capacity of the Aox protein. In the same cultivar, this gene was under-expressed in salt stress conditions with poor effect on the protein level. In the sensitive cultivar (Vita 5), the transcript level of the VuAox2b was unchanged in response to PEG treatment, even though the protein and the capacity tended to increase. Upon salt stress, the VuAox2b gene was overexpressed. At 100mM NaCl, this VuAox2b gene over-expression led to a higher amount and capacity of Aox. This effect was reduced at 200mMNaCl. Overall, these results suggest complex mechanisms (transcriptional, translational and posttranslational) for Aox regulation in response to osmotic stress.