Fine Mapping and Candidate Gene Prediction of the Quantitative Trait Locus qPL8 for Panicle Length in Rice

Rice panicle is the sink organ where assimilation product accumulates,and its morphology determines the rice yield.Panicle length has been suggested as a yield-related trait,but the genetic factor for its control is still limited.In this study,we carried out fine-mapping of qPL8,a QTL identified for panicle length in our previous work.Near isogenic line(NIL)with qPL8 exhibited elongated panicle without obvious effect on other panicle elements.With five key recombinants from NIL population,the locus was finally narrowed down to a 278-kb region,where 44 genes are annotated.By comparing the genomic sequence of two parents,17 genes were identified with SNPs or InDels variations in the coding region.Expression analysis showed that eight genes were up-regulated in the NIL with qPL8.Considering both the coding variation and expression status,several candidate genes for the locus were identified,and OsMADS37 was raised as the most possible candidate.Interestingly,an expression QTL(eQTL)also resides in the locus,leading to a cluster of gene expression variation in the region.This study will facilitate the application of qPL8 locus in rice breeding for yield potential.

Mapping of QTLs Controlling Panicle Length and Effective Panicle Number of Rice

Panicle length and effective panicle number of rice are closely related to yield. In this experiment, indica V20B as female parent was crossed with javanica CPSLO17 as male parent, recombinant inbred line （RIL） populations were obtained by single seed descent method, and with the RIL populations as mapping populations, QTL mapping and analysis were performed to the two panicle traits, panicle length and effective panicle. A high-density genetic map was constructed with SLAF labels, interval mapping was performed by software Map QTL5 under the threshold of 3.9, and 7 QTLs were detected on 3 chromosomes in total. Among the 7 QTLs, 5 QTLs controlling panicle length （qPLI-1, qPL1-2, qPL6-1, qPI_6-2 and qPL6-3） were located on chromosomes 1 and 6, respectively, and showed the contribution rates of 6.41%, 22.22%, 6.15%, 12.24% and 13.01%, respectively, their effect-increasing loci were mainly from CPSLO17, and qPL1-1 is a new QTL; and 2 QTLs controlling effective panicle number （qPN1 and qPN4） were located on chromosomes 1 and 4, respectively, and exhibited the contribution rates of 13.15% and 8.18%, respectively, and the effect-increasing loci were from parent V2OB. The marking of these loci lays a foundation for further cloning of genes controlling panicle length and effective panicle number and molecular marker-assisted selection.

A natural allele of TAW1 contributes to high grain number and grain yield in rice

Grain number per panicle (GNP) is a complex trait controlled by quantitative trait loci (QTL),directly determining grain yield in rice.Identifying GNP-associated QTL is desirable for increasing rice yield.A rice chromosome segment substitution line (CSSL),F771,which showed increased panicle length and GNP,was identified in a set of CSSLs derived from a cross between two indica cultivars,R498 (recipient) and WY11327 (donor).Genetic analysis showed that the panicle traits in F771 were semidominant and controlled by multiple QTL.Six QTL were consistently identified by QTL-seq analysis.Among them,the major QTL q PLN10 for panicle length and GNP was localized to a 121-kb interval between markers N802 and N909 on chromosome 10.Based on quantitative real-time PCR and sequence analysis,TAWAWA1(TAW1),a known regulator of rice inflorescence architecture,was identified as the candidate gene for q PLN10.A near-isogenic line,NIL-TAW1,was developed to evaluate its effects.In comparison with the recurrent parent R498,NIL-TAW1 showed increased panicle length (14.0%),number of secondary branches (20.9%) and GNP (22.0%),and the final grain yield per plant of NIL-TAW1 was increased by18.6%.Transgenic experiments showed that an appropriate expression level of TAW1 was necessary for panicle development.Haplotype analysis suggested that the favorable F771-type (Hap 13) of TAW1was introduced from aus accessions and had great potential value in high-yield breeding both in indica and japonica varieties.Our results provide a promising genetic resource for rice grain yield improvement.

Constitutive Activation OsbZIP62 Improves Plant Height and Yield through Regulating the Expression of Agronomic Traits Related Genes in Rice

Plant height is an important morphological trait that affects crop yield.Several genes related to plant height and yield have been reported in rice(Oryza sativa L.),however,the molecular mechanism underlying the regulation of these traits is still not completely understood.VP64 is widely used as a transcriptional activator to investigate the biological function of genes encoding transcription factors.Here,we identified a novel bZIP transcription factor OsbZIP62 that is involved in modulating agronomic traits in rice.Overexpression of OsbZIP62-VP64(OsbZIP62V)significantly increases the plant height and yield per plant in rice.RNA-seq analysis showed that some plant height and panicle development related genes(i.e.,OsEATB,OsDSS1 and OsGA3ox2)were up-regulated in OsbZIP62V overexpressing rice plants.Besides,OsbZIP62 could also bind to the promoters of several putative target genes.These results suggested that OsbZIP62 plays a role as transcriptional regulator in regulating the expression of genes associated with agronomic traits,and OsbZIP62 fused with VP64 would be useful in crop genetic modification with improved plant architecture and yield.

Stability of PAC(Psy-2A-Crt I) gene and agronomic traits in the F_(2:3) of IR36/PAC transgenic plants

This study was carried out to evaluate the expression of yellow endosperm color in the progeny of Psy-2A-Crt I（β-carotene gene, PAC） transgenic plants crossed with IR36. The selected 25 lines of F2 progeny exhibited stable expression of yellow endosperm color and high agronomic characteristics. IR36 and PAC transgenic plant of the grain length, width and ratio showed the same tendency of normal distribution. For progeny selection, colorimeters were as employed to distinguish differing visible colors. Correlation analysis was conducted to investigate the relationship between b＊ value and the expression of specific genes. b＊ value was associated with the relative expression of the PAC-Rev and MAR product by real-time PCR and t-test revealed significant difference. Based on this study, correlation between colorimetric values and real-time PCR was effective to detect gene expression. Yellow endosperm progenies represent a new genetic pool that might be useful to increase the genetic diversity of yellow endosperm rice.