Non-functional S-RNases are recruited to cope with phosphate starvation in Nicotiana

HERNÁN J. ROJAS AND ARIEL GOLDRAIJ

Mendoza

Congreso; SAIB Sociedad Argentina de Investigacion en Bioquimica y Biologia Molecular; 2012

SAIB

Plant T2 ribonucleases (RNases) were classified in two subfamilies, a) S-RNases, involved in pollen recognition and rejection of some self-incompatible species and b) S-like-RNases, widely distributed in the plant kingdom and involved in the response to different biotic and abiotic stresses. We have cloned a stylar cDNA from Nicotiana alata with structural traits of S-RNases but without functionality in the self-incompatibility system; therefore, it was denoted as non-S63-RNase. This gene was induced in plants hydroponically grown without Pi, a typical response of S-like-RNases, but not reported yet in other RNases. A 15 amino acid peptide corresponding to the hypervariable region of non-S63-RNase was used to develop a rabbit antibody. The antibody recognized a signal protein of 31 kDa in root extracts from plants grown under Pi starvation. This signal decayed significantly after preincubation of serum with the antigenic peptide providing evidence that the 31 kDa protein was the non-S63-RNase. The induction of non-S63-RNase was rapidly repressed when Pi-starved plants were replaced in a Pi-supplemented medium. In gel RNase-activity showed a band of 31 kDa which was also recognized by the anti-peptide antibody. This result suggested that the non-S63-RNase was induced in an enzymatically active form. To our knowledge this is the first report of a functional role for a non-S-RNase.