Functional Analysis Of GmCry1s In Regulating Shade Avoidance Syndrome In Soybean

Shade avoidance syndrome(SAS)is a plasticity response of plants to shade conditions.In recent years,the molecular mechanisms of the shade avoidance syndrome have been well elucidated in Arabidopsis thaliana.However,mechanisms of crop SAS are still rarely reported.Soybean is an essential oil and feed crop globally and sensitive to changes in the light environment.Although dense planting or intercropping can effectively improve soybean yield.However,it poses risks for soybean SAS and lodging.Therefore,studying soybean shade avoidance syndrome is a meaningful subject.The main results are as follows:In addition to the significant decrease in the R:FR ratio,the blue light intensity is reduced by about 90%under natural shade conditions.The results showed that low R:FR ratio could significantly induce leaves hyponastic movement and petiole elongation under 500 ?mol m-2 sec-1 photosynthetically active radiation(PAR)condition in soybean.While with constant PAR,low blue light dramatically stimulates stem growth and petiole elongation in soybean.These results indicated that soybean photoreceptors might work together to regulate soybean SAS.Compared with wild-type plants,GmCry1b overexpression transgenic plants were more sensitive to blue light signals and could significantly inhibit the stem elongation even under low-blue-light conditions.Instead,Gmcry1s-qm quadruple mutant plants were insensitive to low blue light.They showed a similar elongated phenotype under both WL and LBL conditions,which indicated that GmCry1s is a key photoreceptor in mediating low-blue-light induced soybean SAS.We performed RNA-seq(RNA sequencing)analysis using WT(TianLongl),GmCry1b-YFP overexpression,Gmcryls-qm,and GmCry2s-tm plants.GO(Gene Ontology)results indicated that the gibberellin metabolic pathway genes were significantly enriched in the differentially expressed genes.We found that blue light stimulates GmGA2ox-7a/7b expression through GmCry1s,reduce the content of bioactive gibberellin GA1,and inhibit plant elongation.Overexpression of the GmGA2ox-7a gene completely inhibited the low-blue-light induced soybean SAS.In addition,blue light also caused the accumulation of soybean GmHY5a protein.Using ChIP-qPCR,we found that soybean GmHY5a/5b proteins can specifically bind to the G-box motif of and GmGA2ox-7b genes,and the GmHY5a/5b overexpressing transgenic plants had a short stem.The field trial and agronomic performance of transgenic soybean indicated that GmCry1b overexpression inhibited stems elongation and SAS,which displayed excellent shade tolerance and lodging-resistant.Moreover,its yield was significantly higher than that of wild type plant.The above results show that:light-induced the accumulation of GmHY5a/5b proteins in a blue light-specific manner through GmCry1s,which promoted the expression of GmGA2ox-7a/7b genes and reduced bioactive gibberellin GA1 in vivo.Finally,the transgenic plants showed a short stem.Under low-blue-light conditions,the abundance of GmHY5a protein were significantly decreased,which led to an increase of gibberellin GA1 and induced elongation of soybean stems.Additionally,the GmCry1b overexpression transgenic plants showed significant shade tolerance,provided a promising option to breed lodging-resistant and high yield soybean cultivars in the future.