Regulation of Brassinosteroid Signaling and Salt Resistance by SERK2 and Potential Utilization for Crop Improvement in Rice

Abstract

The complex roles of the steroid hormone brassinosteroids (BRs) in many different yield- and stress-related traits make it difficult to utilize the hormones for crop improvement. Here, we show that SERK2 as a BR signaling component is a potentially useful candidate for BR manipulation in rice. We generated multiple mutant alleles of SERK2 by CRISPR/Cas9 editing and show that knockout of SERK2 results in a compact structure accompanied with increased grain size. SERK2 is localized on plasma membrane and can interact with OsBRI1, the BR receptor, suggesting its conserved role as co-receptor in BR signaling. Consistently, the mutant has impaired BR sensitivity compared to wild type. Notably, the mutant is highly sensitive to salt stress as evaluated by plant survival rate as well as transcriptome analysis, whereas has slightly increased sensitivity to ABA, the stress hormone. By contrast, overexpression of SERK2 significantly enhances grain size and salt stress resistance, importantly, without affecting plant architecture. Furthermore, while salt suppresses SERK2 transcription, the protein is greatly induced by salt stress. Taken together, we propose that the adverse condition induces SERK2 accumulation to enhance early BR signaling on plasma membrane in favor of the anti-stress response. Our results illustrate the great potentials of specific BR components such as SERK2 for crop improvement by utilizing flexible strategies.

Regulation of Plant Responses to Salt Stress

“…The BR receptor SERK2 significantly enhances grain size and salt resistance in rice. Adverse high salinity conditions induce SERK2 accumulation to enhance early BR signaling on the plasma membrane to defend against the stress [ 85 ].…”

Hormonal crosstalk in regulating salinity stress tolerance in graminaceous crops

“…Various BR signaling components manipulate the BRs, resulting in multiple responses. In rice, Somatic embryogenesis receptor kinase 2 ( SERK2 ) expression is enhanced under salt stress, which eventually activates BR signaling, thereby improves salt tolerance (Dong et al, 2020). BRs are reported to regulate MAPK signaling to decrease the stomatal conductance, thereby improving salt tolerance.…”

“…Further, in rice, knockout of SERK2 , a BR signaling component, showed enhanced salt sensitivity. However, the overexpression of SERK2 resulted in improved salt resistance and enhanced grain size without influencing the rice seedling architecture (Dong et al, 2020). Thus, manipulating the BR signaling by overexpressing SERK2 improved growth in rice under salt stress conditions.…”

McMYB4 improves temperature adaptation by regulating phenylpropanoid metabolism and hormone signaling in apple

“…Moreover, in red mango fruit, RNA-seq analysis suggested that the genes involved in the brassinosteroid signaling pathway were upregulated and increased plant resistance to light 46 . In addition, in brassinosteroid signaling, SERK2, as a BR signaling component, could interact with OsBRI1 to promote early BR signaling and enhance grain size and salt tolerance 47 . Therefore, flavonol biosynthesis and BR signaling have important functions in plant resistance, and during this process, ROS act as plant signals to respond to environmental changes 48 .…”