Novel Bifunctional Nucleases, OmBBD and AtBBD1, Are Involved in Abscisic Acid-Mediated Callose Deposition in Arabidopsis

Abstract

Screening of the expressed sequence tag library of the wild rice species Oryza minuta revealed an unknown gene that was rapidly and strongly induced in response to attack by a rice fungal pathogen (Magnaporthe oryzae) and an insect (Nilaparvata lugens) and by wounding, abscisic acid (ABA), and methyl jasmonate treatments. Its recombinant protein was identified as a bifunctional nuclease with both RNase and DNase activities in vitro. This gene was designated OmBBD (for O. minuta bifunctional nuclease in basal defense response). Overexpression of OmBBD in an Arabidopsis (Arabidopsis thaliana) model system caused the constitutive expression of the PDF1.2, ABA1, and AtSAC1 genes, which are involved in priming ABA-mediated callose deposition. This activation of defense responses led to an increased resistance against Botrytis cinerea. atbbd1, the knockout mutant of the Arabidopsis ortholog AtBBD1, was susceptible to attack by B. cinerea and had deficient callose deposition. Overexpression of either OmBBD or AtBBD1 in atbbd1 plants complemented the susceptible phenotype of atbbd1 against B. cinerea as well as the deficiency of callose deposition. We suggest that OmBBD and AtBBD1 have a novel regulatory role in ABA-mediated callose deposition.

Identification of a Novel Jasmonate-Responsive Element in the AtJMT Promoter and Its Binding Protein for AtJMT Repression

“…Sequence analysis of the AtBBD1 protein family had previously shown that the AtBBD1 proteins contain several conserved domains, including a highly conserved region (HCR), a domain of unknown function 151 (DUF151), and a UV responsive (UVR) domain at the C-terminus [50]. However, this analysis did not identify a known DNA-binding motif; therefore, we tested whether different domains of AtBBD1 had DNA-binding activity.…”

“…Clones were sequenced from positive colonies and sequence analysis showed that multiple positive clones corresponded to AtBBD1 (Figure S1). AtBBD1 is an Arabidopsis homologue of the Oryza minuta bifunctional nuclease in basal defense response ( OmBBD1 ), which acts in abscisic-acid (ABA)-dependent callose deposition [50]. The Arabidopsis thaliana genome also contains an AtBBD1 homologue, AtBBD2, with 81% amino acid sequence identity to AtBBD1 (Figure S2C).…”

I. Primexine development in Passiflora racemosa Brot.: overlooked aspects of development

“…Callose probably promotes structureforming processes at the interface. This is in accordance with the data on callose-deficiency mutants (Dong et al 2005;Nishikawa et al 2005;You et al 2010).…”

Transcriptome Analysis Reveals Crosstalk of Responsive Genes to Multiple Abiotic Stresses in Cotton (Gossypium hirsutum L.)

“…Bifunctional Nucleases (BFNs) have both RNase and DNase activities. Two BFNs in basal defense response 1 (BBD1) from Oryza minuta and Arabidopsis , OmBBD1 and AtBBD1 respectively, were investigated recently, and it was reported that these two proteins took regulatory roles in ABA-mediated callose deposition to set up an initial defense barrier against pathogenesis [74]. Interestingly, we found 2 BBD1 proteins from our microarray data, it suggests the existence of shared defensing pathways and transduction signals to abiotic and biotic stresses in plant.…”