Abstract
Blue-light inhibitors of cryptochromes (BICs) promote hypocotyl elongation by suppressing the activity of cryptochromes in Arabidopsis. Nevertheless, the roles of BICs in other plant species are still unclear. Here we investigate their functions by genetic overexpression and CRISPR/Cas9 engineered mutations targeting the six GmBIC genes in soybean. We showed that the GmBICs overexpression (GmBICs-OX) lines strongly promoted stem elongation, while the single, double, and quadruple mutations in the GmBIC genes resulted in incremental dwarfing phenotypes. Furthermore, overexpression of GmBIC2a abolished the low blue light (LBL)-induced stem elongation, demonstrating the involvement of GmBICs in regulating cryptochrome-mediated LBL-induced shade avoidance syndrome (SAS). The Gmbic1a1b2a2b quadruple mutant displayed reduced stem elongation under LBL conditions, which was reminiscent of the GmCRY1b-OX lines. Taken together, this study provided essential genetic resources for elucidating GmBICs functional mechanisms and breeding of shade-tolerant soybean cultivars in future.
Highlights
Arabidopsis thaliana harbors two cryptochromes, CRY1 and CRY2, which mediate the bluelight-dependent inhibition of hypocotyl elongation and photoperiodic flowering, respectively (Ahmad and Cashmore, 1993; Guo et al, 1998; Sancar, 2000; Cashmore, 2003)
The alignments of the protein sequences indicate that all the soybean and Arabidopsis Blue-light inhibitors of cryptochromes (BICs) proteins contain the conserved Cryptochrome Interacting Domain (CID) (Wang Q. et al, 2016; Ma et al, 2020), implying that the soybean GmBICs may function as the Arabidopsis BICs in the cryptochrome mediated blue light signaling pathway (Supplementary Figure 1)
We reported that GmCRY1s mediate the low blue light (LBL) signal to regulate stem elongation in soybean
Summary
Arabidopsis thaliana harbors two cryptochromes, CRY1 and CRY2, which mediate the bluelight-dependent inhibition of hypocotyl elongation and photoperiodic flowering, respectively (Ahmad and Cashmore, 1993; Guo et al, 1998; Sancar, 2000; Cashmore, 2003). Three FOX lines overexpressing the same gene were identified to be phenocopy with the cry1cry mutant, including elongated hypocotyl under blue light, less anthocyanin accumulation, and delayed flower time under long-day conditions (Wang Q. et al, 2016). The casual gene and its homologous gene in Arabidopsis were named as Blue-light Inhibitor of Cryptochromes 1 (BIC1, At3G52740) and BIC2 (At3G44450), respectively. Both BIC1 and BIC2 are located in the cytosol and the GmBICs Regulate Stem Elongation nucleus containing a highly conserved Cryptochrome Interacting Domain (CID) among different species. Extensive studies showed that BIC interacts with the PHR domain of CRYs through the CID domain to inhibit the photoactivation or post-photoactivating processes of CRYs, including dimerization, phosphorylation, protein interaction, formation of photobodies, and degradation (Wang Q. et al, 2016; Ma et al, 2020; Wu et al, 2021)
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