Vacuolar cysteine proteases of wheat (Triticum aestivum L) common to leaf senescence induced by different factors

MARTÍNEZ DANA; BARTOLI CARLOS GUILLERMO; GRBIC VOJISLAVA; GUIAMET JUAN JOSÉ

JOURNAL OF EXPERIMENTAL BOTANY

Oxford University Press

Lugar: Lancaster; Año: 2007 vol. 58 p. 1099 - 1107

0022-0957

Cellular proteins are extensively degraded during leaf senescence, and this correlates with up-regulation of protease gene expression, particularly cysteine proteases. The objectives of this work were –1 to detect cysteine proteases associated with senescence of wheat leaves under different conditions and –2 to find out their subcellular location.  Activity labeling of cysteine proteases with the biotinylated inhibitor DCG-04 detected five bands at 27, 36, 39, 42 and 46 kDa in leaves of wheat senescing under continuous darkness. In gel activity assays showed that these proteases are only active in an acid milieu (pH 4), and their activity increased several fold in senescing leaves. Fractionation experiments showed that these senescence-associated cysteine proteases localize to a vacuolar-enriched fraction. The same vacuolar cysteine proteases increased in activity in attached flag leaves senescing naturally during post-anthesis, and in attached leaves of plants subjected to a water deficit period. Thus, the activity of the vacuolar cysteine proteases detected in this work is associated with developmental (post-anthesis) senescence and with senescence induced by stress factors (i.e., protracted darkness or drought). This suggests that vacuoles are involved in senescence-associated cellular degradation, and that different senescence-inducing factors converge on a single degradation pathway.