OsADR3 increases drought stress tolerance by inducing antioxidant defense mechanisms and regulating OsGPX1 in rice(Oryza sativa L.)

The C (Cys) 2H (His) 2-type transcription factor is one of the most important transcription factors in plants and plays a regulatory role in the physiological responses of rice to abiotic stresses.A novel rice C2H2-type zinc finger protein,abscisic acid (ABA)-drought-reactive oxygen species (ROS) 3 (OsADR3),was found to confer drought stress tolerance by enhancing antioxidant defense and regulating Os GPX1.Overexpression of OsADR3 in rice increased tolerance to drought stress by increasing ROS scavenging ability and ABA sensitivity.In contrast,CRISPR/Cas9-mediated knockout of osadr3 increased the sensitivity of rice to drought and oxidative stress.An exogenous ROS-scavenging reagent restored the droughtstress tolerance of osadr3-CRISPR plants.Global transcriptome analysis suggested that OsADR3 increased the expression of Os GPX1 under drought stress.Electrophoretic mobility shift,yeast one-hybrid,and dualluciferase reporter assays revealed that OsADR3 modified the expression of Os GPX1 by directly binding to its promoter.Knockdown of Os GPX1 repressed ROS scavenging ability under drought stress in OsADR3-overexpression plants.These findings suggest that OsADR3 plays a positive regulatory role in droughtstress tolerance by inducing antioxidant defense and associated with the ABA signaling pathway in rice.

Elite sd1 alleles in japonica rice and their breeding applications in northeast China

The Green Revolution gene sd1 has been used extensively in modern rice breeding,especially in indica cultivars.However,elite sd1 alleles and related germplasm resources used for japonica rice breeding have not been identified,and extensive efforts are needed for japonica rice breeding to obtain new dwarfing sources.Data from MBKbase-Rice revealed seven sd1 haplotypes in indica and four in japonica rice.Two new sd1 alleles were identified in indica rice.In 295 japonica accessions from northeast Asia,except for the weak functional allele SD1-EQ,sd1-r was the major allele,reducing plant height in comparison with SD1-EQ.Japonica germplasm resources carrying reported sd1 alleles were identified by genotype searching and further verified by literature search,genealogical analysis,and d Caps markers.Pedigrees and geographic distribution showed that sd1-r is an excellent allele widely used in northern China and Tohoku in Japan,and sd1-j is commonly used in east China and Kyushu in Japan.Dongnong-and Xiushui-series cultivars carrying sd1-r and sd1-j,respectively,are essential branches of the backbone parents of Chinese japonica rice,Akihikari and Ce21,with the largest number of descendants and derived generations.In semi-dwarf japonica rice breeding,sd1-d was introgressed into Daohuaxiang 2(DHX2).Dwarf and semi-dwarf lines carrying sd1-d were selected and designated as 1279 and 1280,respectively,after withstanding typhoon-induced strong winds and heavy rains in 2020,and are anticipated to become useful intermediate materials for future genetic research and breeding.This work will facilitate the introduction,parental selection,and marker-assisted breeding,and provide a material basis for the next step in identifying favorable genes that selected together with the sd1 alleles in japonica backbone parents.

Combinations of Hd2 and Hd4 genes determine rice adaptability to Heilongjiang Province, northern limit of China

Heading date is a key trait in rice domestication and adaption, and a number of quantitative trait loci（QTLs）have been identified. The rice（Oryza sativa L.） cultivars in the Heilongjiang Province, the northernmost region of China,have to flower extremely early to fulfill their life cycle.However, the critical genes or different gene combinations controlling early flowering in this region have not been determined. QTL and candidate gene analysis revealed that Hd2/Ghd7.1/Os PRR37 plays a major role in controlling rice distribution in Heilongjiang. Further association analysis with a collection of rice cultivars demonstrated that another three major QTL genes（Hd4/Ghd7, Hd5/DTH8/Ghd8, and Hd1）also participate in regulating heading date under natural long day（LD） conditions. Hd2/Ghd7.1/Os PRR37 and Hd4/Ghd7 are two major QTLs and function additively. With the northward rice cultivation, the Hd2/Ghd7.1/Os PRR37 and Hd4/Ghd7 haplotypes became non-functional alleles. Hd1 might be non-functional in most Heilongjiang rice varieties,implying that recessive hd1 were selected during local rice breeding. Non-functional Hd5/DTH8/Ghd8 is very rare, but constitutes a potential target for breeding extremely early flowering cultivars. Our results indicated that diverse genetic combinations of Hd1, Hd2, Hd4, and Hd5 determined the different distribution of rice varieties in this northernmost province of China.