Molecular Mechanism Of Rice Latitude Adaptation

Rice is the staple food for about half the world’s population,and its yield is crucial for food security.The heading date is closely related to the rice yield.The photoperiod pathway is essential for rice to regulate flowering,which affects the expression of the florigen genes Heading date-3a(Hd3a)and RICE FLOWERING LOCUS T1(RFT1)to affect the heading date.With global warming,the growing areas of crops are expanding to higher latitudes.The daylength is different in various latitudes,so the photosensitivity of crops is related to the latitude.We have established a method to quickly detect rice photosensitivity and predict rice latitude adaptability to speed up the selection of rice latitude adaptability.First,we tested the genotypes of 12 important photoperiod genes in 44 sterile lines and 70 restorer lines,such as Heading date 1(Hd1),DAYS TO HEADING 8(DTH8),Grain number,plant height and heading date 7(Ghd7),Grain number,plant height and heading date 7.1(Ghd7.1/DTH7/OsPRR37).Interestingly,there are homozygous mutation types in Hd1 and DTH8 in hybrid indica rice.Hd1hd1 dth8dth8 and hd1hdl DTH8dth8 are the two main genotypes of hybrid indica rice to improve latitude adaptability in East Asia.Secondly,in order to explore how Hdl,DTH8,Ghd7 and DTH7 affect the latitude adaptability and daylength-sensing of rice,we established a Daylength-sensing based Environment Adaptation Simulator(DEAS).Through DEAS step 1 to detect the expression of florigen genes Hd3a and RFT1 under 7 different daylength,that is,daylength-sensing.The wild-type japonica cultivar Dongjin recognizes the critical daylength of 13.5h;hdl,dth8 single mutant recognizes the critical daylength of 14h;hdl dth8,ghd7,hdl dth8 ghd7 recognizes the gradual daylength and weaken the photosensitivity.The DTH7 mutation also changed the daylength-sensing of rice to a great extent.These data confirm that DTH8-Hd1-Ghd7-DTH7 is a core module that mediates multiple daylength-sensing processes in rice.Finally,we use the florigen gene expression data under various daylength obtained from DEAS step 1,and then predict the heatmap of florigen gene expression in different latitudes through the DEAS step 2 to predict latitude adaptation.At the same time,in order to evaluate the accuracy of DEAS prediction,we tested the gene expression data of florigen in simulated classes and fields in different periods.According to different methods to evaluate the accuracy of DEAS prediction,it is found that the prediction accuracy of DEAS for rice florigen expression is about 70%.At the same time,we also proved the application potential of DEAS in maize and soybean.In summary,we have successfully established a set of methods to predict the latitude adaptability of rice.Applying these methods to rice breeding programs can accelerate crop latitude adaptation selection and promote sustainable agricultural development.