Enhancing rice grain production by manipulating the naturally evolved cis-regulatory element-containing inverted repeat sequence of OsREM20

Grain number per panicle(GNP)is an important agronomic trait that contributes to rice grain yield.Despite its importance in rice breeding,the molecular mechanism underlying GNP regulation remains largely unknown.In this study,we identified a previously unrecognized regulatory gene that controls GNP in rice,Oryza sativa REPRODUCTIVE MERISTEM 20(OsREM20),which encodes a B3 domain transcription factor.Through genetic analysis and transgenic validation we found that genetic variation in the CArG box-containing inverted repeat(IR)sequence of the OsREM20 promoter alters its expression level and contributes to GNP variation among rice varieties.Furthermore,we revealed that the IR sequence regulates OsREM20 expression by affecting the direct binding of OsMADS34 to the CArG box within the IR sequence.Interestingly,the divergent pOsREM20IR and pOsREM20ΔIR alleles were found to originate from different Oryza rufipogon accessions,and were independently inherited into the japonica and indica subspecies,respectively,during domestication.Importantly,we demonstrated that IR sequence variations in the OsREM20 promoter can be utilized for germplasm improvement through either genome editing or traditional breeding.Taken together,our study characterizes novel genetic variations responsible for GNP diversity in rice,reveals the underlying molecular mechanism in the regulation of agronomically important gene expression,and provides a promising strategy for improving rice production by manipulating the cis-regulatory element-containing IR sequence.

Relationship between Mutation of IR in the mtr System of Neisseria Gonorrhoeae and Multiple Antibiotic Resistance

To study the relationship between mutation of the inverted repeat sequence （IR） in the multiple transferable resistant system （mtr） of Neisseria gonorrhoeae （NG） and its multiple antibiotic resistance, minimal inhibitory concentrations （MICs） for the clinically isolated strains were tested by agar-dilution-method. The mtr system＇s IR gene of NG was sequenced after amplification by polymerase chain reaction （PCR）. Either two susceptive or five penicillin-resistant strains had no base mutation in IR gene, while all of the 13 strains with multiple-antibiotic-resistance had a singlebase deletion （A/T）. The result suggests that a single-base deletion of the thirteen-base IR sequence in mtr system of NG might result in multiple antibiotic resistance but is not associated with single antibiotic resistance.