Identification of a major quantitative trait locus and its candidate underlying genetic variation for rice stigma exsertion rate

Stigma exsertion in male sterile lines of hybrid rice is important for seed yield.In the present study, ZS616 [Oryza sativa subsp.Xian(indica)], a male sterile line with a stigma exsertion rate(SER) as high as 94.5%, was crossed to DS552, a japonica line with almost no exserted stigmas.F3 plants with extremely low and high SER were sequenced to identify SER-associated quantitative trait loci(QTL).A major QTL for SER, qSER-3.1, was identified along with other QTL on chromosome 3 in a 3.9 Mb region.A total of 307 nonsynonymous single-nucleotide polymorphisms(SNPs) and 27 frame-shift insertion/deletions(InDels)differentiating ZS616 and DS552 were identified in the region containing qSER-3.1.Most SNPs(294) and InDels(25) were excluded after further analysis because they were shared by ZS616 and low(<2.0%) SER accessions in the Huazhong Agricultural University(HAU) core rice collection.Association analysis using the full HAU collection identified a 17-bp InDel in OS03 G0689400 as the most likely causal genetic variant underlying qSER-3.1.ZS616-type accessions(n = 54, with the 17-bp insertion) in the HAU collection had minimum(16.5%)and mean(39.6%) SERs significantly greater than those(n = 424) without the insertion(with minimum and mean SERs of 0.2% and 20.6%, respectively).Thus, this study identified a major QTL for stigma exsertion and revealed the mutation in a candidate gene for the QTL.

Nuclear translocation of OsMFT1 that is impeded by OsFTIP1 promotes drought toleranee in rice

Drought is the leading environmental threat affecting crop productivity,and plants have evolved a series of mechanisms to adapt to drought stress.The FT-interacting proteins(FTIPs)and phosphatidylethanola mine.binding proteins(PEBPs)play key roles in developmental processes,whereas their roles in the regulation of stress response are still largely unknown.Here,we report that OsFTIP1 negatively regulates drought response in rice.We showed that OsFTIP1 interacts with rice MOTHER OF FT AND TFL1(OsMFT1),a PEBP that promotes rice tolerance to drought treatment.Further studies discovered that OsMFT1 interacts with two key drought-related transcription factors,OsbZIP66 and OsMYB26,regulating their binding capacity on drought-related genes and thereby enhancing drought toleranee in rice.Interestingly,we found that OsFTIP1 impedes the nucleocytoplasmic translocation of OsMFT1,implying that dynamic modulation of drought-responsive genes by the OsMFT1-OsMYB26 and OsMFT1-OsbZIP66 complexes is integral to OsFTIP1-modulated nuclear accumulation of OsMFT1.Our findings also suggest that OsMFT1 might act as a hitherto unknown nucleocytoplasmic trafficking signal that regulates drought tolerance in rice in response to environmental signals.

Current insights on rice(Oryza sativa L.)bakanae disease and exploration of its management strategies

Bakanae is an emerging rice disease caused by the seed-and soil-borne pathogen Fusarium fujikuroi.It is becoming a more serious threat to sustainable rice production throughout rice-growing regions.Bakanae disease infection is responsible for high yield losses ranging from 3%to 95%,and disease incidence varies based on the region and cultivars.Hence,understanding the nature of the pathogen,its pathogenicity,disease epidemiology,symptoms,host–pathogen interaction,and the role of secondary metabolites in the disease cycle will be helpful in the development of effective and sustainable management strategies.However,very few comprehensive studies have described the details of rice bakanae disease.Thus,in this review we summarize and discuss in detail the information available from 1898 to 2023 on various critical facets of bakanae disease,and provide perspectives on future research.

Melatonin activates the OsbZIP79–OsABI5 module that orchestrates nitrogen and ROS homeostasis to alleviate nitrogen-limitation stress in rice

Melatonin(Mel)has previously been reported to effectively alleviate nitrogen-limitation(N-L)stress and thus increase nitrogen-use efficiency(NUE)in several plants,but the underlying mechanism remains obscure.Here,we revealed that OsbZIP79(BASIC LEUCINE ZIPPER 79)is transcriptionally activated under N-L conditions,and its expression is further enhanced by exogenous Mel.By the combined use of omics,genetics,and biological techniques,we revealed that the OsbZIP79–OsABI5(ABSCISIC ACID INSENSITIVE 5)module stimulated regulation of reactive oxygen species(ROS)homeostasis and the uptake and metabolismof nitrogen under conditions of indoor nitrogen limitation(1/16 normal level).OsbZIP79 activated the transcription of OsABI5,and OsABI5 then bound to the promoters of target genes,including genes involved in ROS homeostasis and nitrogen metabolism,activating their transcription.This module was also indispensable for upregulation of several other genes involved in abscisic acid catabolism,nitrogen uptake,and assimilation under N-L and Mel treatment,although these genes were not directly transactivated by OsABI5.Field experiments demonstrated that Mel significantly improved rice growth under low nitrogen(L-N,half the normal level)by the same mechanism revealed in the nitrogen-limitation study.Mel application produced a 28.6%yield increase under L-N and thus similar increases in NUE.Also,two OsbZIP79-overexpression lines grown in L-N field plots had significantly higher NUE(+13.7%and+21.2%)than their wild types.Together,our data show that an OsbZIP79–OsABI5 module regulates the rice response to N insufficiency(N limitation or low N),which is important for increasing NUE in rice production.