Arabidopsis CK2 family gene CKB3 involved in abscisic acid signaling

CKB3 is a regulatory (beta) subunit of CK2. In this study Arabidopsis thaliana homozygous T-DNA mutant ckb3 was studied to understand the role of CKB3 in abscisic acid (ABA) signaling. The results shown: CKB3 was expressed in all organs and the highest expression in the seeds, followed by the root. During seed germination and root growth the ckb3 mutant showed reduced sensitivity to ABA. The ckb3 mutant had more stomatal opening and increased proline accumulation and leaf water loss. The expression levels of number of genes in the ABA regulatory network had changed. This study demonstrates that CKB3 is an ABA signaling-related gene and may play a positive role in ABA signaling.

The Arabidopsis GPI-Anchored LTPg5 Encoded by At3g22600 Has a Role in Resistance against a Diverse Range of Pathogens

Arabidopsis contains 34 genes for glycosylphosphatidylinositol (GPI)-anchored LTPg proteins. A motif analysis has placed these into four groups. With one exception, all are produced with a signal peptide and are most likely attached to the cell membrane via the GPI anchor. Several of the LTPg genes across the four groups are downregulated in syncytia induced by the beet cyst nematode Heterodera schachtii. We have here studied At3g22600 encoding LTPg5, which is the most strongly downregulated LTPg gene. It is mainly expressed in roots, and a promoter::GUS line was used to confirm the downregulation in syncytia and also showed downregulation in galls of the root knot nematode Meloidogyne incognita. In contrast, infection with bacteria (Pseudomonas syringae) and fungi (Botrytis cinerea) led to the induction of the gene in leaves. This diverse regulation of LTPg5 indicated a role in resistance, which we confirmed with overexpression lines and a T-DNA mutant. The overexpression lines were more resistant to both nematode species and to P. syringae and B. cinerea, while a knock-out mutant was more susceptible to H. schachtii and P. syringae. Thus, LTPg5 encoded by At3g22600 is part of the Arabidopsis resistance mechanism against pathogens. LTPg5 has probably no direct antimicrobial activity but could perhaps act by associating with a receptor-like kinase, leading to the induction of defense genes such as PR1.

APC allele-specific expression in carriers of Ashkenazi Jewish mutation I1307K

e22181 Background: I1307K is a missense APC variant with incomplete penetrance that has been found in 6% of Jewish Ashkenazi population and confers a two-fold increased risk to develop multiple adenomas and colorectal tumours. It is believed that it creates a hypermutable region within the gene that leads to an accumulation of mutations. It remains unknown whether the presence of this mutation modifies APC expression. Our goal was to study whether allele-specific expression (ASE) of I1307K is present at the germline and tumoral level. Methods: Paired germline/carcinoma RNA and DNA was studied from eleven I1307K carriers. To analyze changes in the mutant/wt allelic ratio we used single nucleotide primer extension (SNuPE) for the I1307K and the rs2229992 APCcoding SNP. Fourteen controls were also analyzed. Results: No germline allele specific expression was found in I1307K carriers (range=0.954–1.173). Significant ASE was observed in 8 of the 10 carcinomas analyzed. In 4 cases the I1307K allele was overexpressed (range=2.51–9.51) and in 4 cases was underexpressed (range=0.09–0.28). Tumor ASE correlated with the DNA mutant/wt allelic dose. Conclusions: I1307K variant is not associated with allelic specific expression at the germline level. I1307K overexpression is not selected for during tumor progression. No significant financial relationships to disclose.