Abstract:

Sucrose non-fermenting related protein kinases (SnRKs) are a ubiquitous Ser/Thr protein kinase in the plant kingdom. These kinases play important roles in plant growth, development, metabolism and resistance to environmental stresses. The soybean (Glycine max L.) genome has four SnRK1 genes, of which GmSnRK1.1 and GmSnRK1.2 are predominant and participate in multiple stress response pathways. To dissect the mechanism of the role of GmSnRK1.1 and GmSnRK1.2 proteins in response to ABA and alkaline stresses, we constructed a dual-gRNA CRISPR vector to specifically knock out GmSnRK1.1 and GmSnRK1.2. The resultant constructs were transformed into soybean cotyledon nodes to induce hairy roots by agrobacteria (Agrobacterium rhizogenes). The soybean hairy roots obtained were genotyped, and the results showed that GmSnRK1.1 and GmSnRK1.2 were efficiently doubly knocked out in 48.6% hairy roots. We also generated control hairy roots that over-expressed GmSnRK1. The materials were treated with 25 μmol/L ABA for 15 days and the results showed that the growths of wild-type and GmSnRK1 over-expressed roots were significantly inhibited than GmSnRK1.1 GmSnRK1.2 double-knockout roots, as the controls displayed less root lengths and fresh weights. However, after treating with 50 mmol/L NaHCO₃ for 15 days, we found that the growths of GmSnRK1.1 GmSnRK1.2 double-knockout roots were significantly inhibited than the wild-type and GmSnRK1 over-expressed control roots, as the knockout groups contained less root lengths and fresh weights. These results implied that the GmSnRK1.1 GmSnRK1.2 double knockout mitigated hairy root sensitivity to ABA and resistance to alkaline stress. Taken together, we established the CRISPR/Cas9 system to perform gene double knockout in the soybean and by using this technique, we determined the roles of GmSnRK1.1 and GmSnRK1.2 in response of abiotic stresses.

Key words: soybean, CRISPR/Cas9, GmSnRK1.1, GmSnRK1.2, ABA signal, alkaline resistance