ABA-CsABI5-CsCalS11 module upregulates Callose deposition of citrus infected with Candidatus Liberibacter asiaticus.

Huanglongbing (HLB) primarily caused by Candidatus Liberibacter asiaticus (CLas) has been threatening citrus production globally. Under HLB conditions, an excessive accumulation of the polysaccharide callose in citrus phloem occurs, leading to phloem blockage and starch accumulation in leaves. The callose production is controlled by callose synthases (CalS), which have multiple members within plants. However, the knowledge of callose production in the citrus upon infection with CLas is limited. In this study, we firstly identified 11 CalSs in the Citrus sinensis genome through bioinformatics and found the expression pattern of CsCalS11 exhibited a positive correlation with callose deposition in CLas-infected leaves (correlation coefficient of 0.77, P ≤ 0.05). Knockdown of CsCalS11 resulted in a reduction of callose deposition and starch accumulation in CLas-infected citrus. Interestingly, we observed significantly higher concentrations of abscisic acid (ABA) in HLB-infected citrus leaves compared to uninfected ones. Furthermore, the expressions of CsABI5, CsPYR, and CsSnRK2 in the ABA pathway substantially increased in citrus leaves upon CLas infection. Additionally, the expression of CsCalS11 was significantly upregulated in citrus leaves following the application of exogenous ABA. We confirmed that CsABI5, a pivotal component of the ABA signaling pathway, regulates CsCalS11 expression by binding to its promoter using yeast one-hybrid assay, dual luciferase assay, and transient expression in citrus leaves. In conclusion, our findings strongly suggest that the CsABI5-CsCalS11 module plays a crucial role in regulating callose deposition through the ABA signaling pathway during CLas infection. The results also revealed new function of the ABA signaling pathway in plants under biotic stress.

[Cloning and expression pattern of erk2 gene in Inner Mongolia Cashmere goat].

The study aims at cloning the CDS fragment of erk2 gene cDNA in Inner Mongolia Cashmere Goat and analyzing its tissue-specific expression, erk2 gene cDNA was cloned by RT-PCR. The nucleotide sequence was analyzed by Blast and amino acid sequence was analyzed by online softwares SMART and Psite. The tissue-specific expression pattern of erk2 was analyzed by quantitative RT-PCR. The expression of erk2 in testis of goat was detected by Immunohistochemistry. The cloned erk2 gene cDNA (GenBank Accession No. JX569765) was 1 083 bp in length, including a complete ORF encoding 360 amino acids residues. The amino acid sequence shares 100% identity with the Bos Taurus ERK2 (Bos Taurus BC133588.1). Analysis by SMART suggests that the encoded protein contained a "TEY" structure and an S-TKc domain possessing serine/threonine kinase catalytic activity. Analysis with Psite indicates one cAMP-/cGMP-dependent protein kinase phosphorylation site, 3 protein kinase C phosphorylation sites, 5 casein kinase II phosphorylation sites, 2 protein kinases ATP-binding region signatures and one serine/threonine protein kinases active-site signature in this protein. Analysis by Psort (k-NN prediction) suggestes that this protein most probably is localized in cytoplasm. The results of quantitative RT-PCR show that the expression of erk2 mRNA was higher in heart, skin and breast, whereas lower in spleen and kidney. ERK2 protein was detected in testis by immunohistochemistry.