SASP, a Senescence-Associated Subtilisin Protease, is involved in reproductive development and determination of silique number in Arabidopsis

MARTÍNEZ D.E; BORNIEGO, M.L.; BATTCHIKOVA N.; ARO, E.M.; TYYSTJAERVI E.; GUIAMET J.J

JOURNAL OF EXPERIMENTAL BOTANY

OXFORD UNIV PRESS

Lugar: Oxford; Año: 2015 vol. 66 p. 166 - 174

0022-0957

Senescence involves increased expression of proteases, which may participate in nitrogen recycling or cellular signalling. Two-dimensional zymograms detected two spots with increased proteolytic activity in senescing leaves of Arabidopsis thaliana. A proteomic analysis revealed that both spots correspond to a subtilisin protease coded by At3g14067, hereafter called ?Senescence-Associated Subtilisin Protease? (SASP). SASP mRNA levels and enzyme activity increase during leaf senescence, both in leaves senescing during the vegetative or the reproductive phase of the plant life cycle, but this increase is more pronounced in reproductive plants. SASP is expressed in all above-ground organs, but not in roots.Putative AtSASP orthologs were identified in dicot and monocot crop species. A phylogenetic analysis shows AtSASP and its putative orthologs clustering in one discrete group of subtilisin proteases in which no other Arabidospsis subtilisin protease is present. Phenotypic analysis of two knock out lines for SASP showed that mutant plants develop more inflorescence branches during reproductive development. Both AtSASP and its putative rice ortholog (OsSASP) were constitutively expressed in sasp-1 to complement the mutant phenotype. At maturity, sasp-1 plants produced 25% more inflorescence branches and siliques than either the wild type or the rescued lines. These differences were mostly due to an increased number of second and third order branches. The increased number of siliques was compensated for by a small decrease (5%) in seed size. SASP down-regulates branching and silique production during monocarpic senescence, and its function is at least partially conserved between Arabidopsis and rice.