Pea albumin 1b (PA1b), an entomotoxic cysteine-rich peptide, protects transgenic rice seeds against the stored-product pest Sitophilus oryzae : [P373]

Pea albumin 1b (PA1b), a plant entomotoxin isolated from Pisum sativum (Delobel et al., 1998), was used to generate transgenic rice lines resistant to the stored-product insect pest Sitophilus oryzae. PA1b is the result of the post-transcriptional cleavage of the albumin polyprotein PA1 which also leads to the release of a second peptide, PA1a (53 amino acids). PA1b is a cysteine-rich peptide of 37 amino acids belonging to the cystine-knot family (Jouvensal et al., 2003). In pea, different nucleotidic sequences (Louis et al., 2004) and protein extracts (Taylor et al., 2004) corresponding to PA1b have been isolated underlying the multigenic character of this new family of plant entomotoxin. Two isoforms of pa1 gene (AJ574794 and AJ574795), placed under the control of the maize ubiquitin promoter, were introduced in rice (cv. Zhong Zuo 321) by Agrobacterium tumefaciens-mediated transformation (Sallaud et al., 2003) and studied separately. 24 T0 events of each isoform were regenerated and characterized by RT-PCR and Southern blot. T1 and T2 seeds were analyzed by Near-Infrared Spectroscopy (NIRS) and by in situ western hybridization (Qu et al., 2003). The latter technique allowed to localize PA1b accumulation in embryo and aleurone layer. Resistance of T2 elite lines was tested in bioassay by feeding 20 rice weevil adults with 5 transgenic seeds. Maximum of mortality was raised by line 30.16 after 5 days (AJ574795) and by line 55.19 after 4 days (AJ574794) of bioassay. Resistance of T3 seeds will be examined in selected homozygous T2 lines. (Résumé d'auteur