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Summary: Seed vigour, including rapid, uniform germination and robust seedling establishment under various field conditions, is becoming an increasingly essential agronomic trait for achieving high yield in crops. However, little is known about this important seed quality trait. In this study, we performed a genome‐wide association study to identify a key transcription factor ZmRap2.7, which regulates seed vigour through transcriptionally repressing expressions of three ABA signalling genes ZmPYL3, ZmPP2C and ZmABI5 and two phosphatidylethanolamine‐binding genes ZCN9 and ZCN10. In addition, ZCN9 and ZCN10 proteins could interact with ZmPYL3, ZmPP2C and ZmABI5 proteins, and loss‐of‐function of ZmRap2.7 and overexpression of ZCN9 and ZCN10 reduced ABA sensitivity and seed vigour, suggesting a complex regulatory network for regulation of ABA signalling mediated seed vigour. Finally, we showed that four SNPs in ZmRap2.7 coding region influenced its transcriptionally binding activity to the downstream gene promoters. Together with previously identified functional variants within and surrounding ZmRap2.7, we concluded that the distinct allelic variations of ZmRap2.7 were obtained independently during maize domestication and improvement, and responded separately for the diversities of seed vigour, flowering time and brace root development. These results provide novel genes, a new regulatory network and an evolutional mechanism for understanding the molecular mechanism of seed vigour. [ABSTRACT FROM AUTHOR]

SUMMARY: Maize plastid terminal oxidase1 (ZmPTOX1) plays a pivotal role in seed development by upholding redox balance within seed plastids. This study focuses on characterizing the white kernel mutant 3735 (wk3735) mutant, which yields pale‐yellow seeds characterized by heightened protein but reduced carotenoid levels, along with delayed germination compared to wild‐type (WT) seeds. We successfully cloned and identified the target gene ZmPTOX1, responsible for encoding maize PTOX—a versatile plastoquinol oxidase and redox sensor located in plastid membranes. While PTOX's established role involves regulating redox states and participating in carotenoid metabolism in Arabidopsis leaves and tomato fruits, our investigation marks the first exploration of its function in storage organs lacking a photosynthetic system. Through our research, we validated the existence of plastid‐localized ZmPTOX1, existing as a homomultimer, and established its interaction with ferredoxin‐NADP+ oxidoreductase 1 (ZmFNR1), a crucial component of the electron transport chain (ETC). This interaction contributes to the maintenance of redox equilibrium within plastids. Our findings indicate a propensity for excessive accumulation of reactive oxygen species (ROS) in wk3735 seeds. Beyond its known role in carotenoids' antioxidant properties, ZmPTOX1 also impacts ROS homeostasis owing to its oxidizing function. Altogether, our results underscore the critical involvement of ZmPTOX1 in governing seed development and germination by preserving redox balance within the seed plastids. Significance Statement: Aside from its established role as a vital regulator of redox states and its involvement in carotenoid metabolism, as observed in Arabidopsis leaves and tomato fruits, this study marks the inaugural exploration into PTOX's function within storage organs lacking a photosynthetic system. Our findings elucidate how ZmPTOX1 significantly impacts protein and starch accumulation in seeds, along with the pace of seed germination. Moreover, it actively maintains redox equilibrium across various stages of seed development and germination. [ABSTRACT FROM AUTHOR]

BACKGROUND: The correct time for harvesting is a key factor contributing to the production of high‐quality maize seeds. We conducted field experiments to harvest seeds at 11 developmental stages for 3 years, to investigate seed vigor traits in three early maturity maize varieties and two late maturity varieties in one location. RESULTS: Significant correlations (r = 0.72 ~ 0.89) were found among six seed‐related traits: standard germination (SG), accelerated aging germination (AAG), cold test germination (CTG), hundred‐seed weight (HSW), seed moisture content (SMC), and ≥ 10 °C accumulated temperature from pollination to harvest (AT10). Analysis of variance showed that harvest stage, year, and variety had significant effects on all traits, and harvest stage displayed the greatest effect. The responses of SG, AAG, CTG, HSW and SMC to harvest stage fitted quadratic models, and AT10 fitted a linear model. From the quadratic models, an ideal harvest time (IHT, the final date to reach maximum SG, AAG, and CTG) could be calculated for each variety. The three early maturity varieties reached their IHT at 54.94–58.44 days after pollination (DAP); the two later maturity varieties reached IHT several days later (at 59.87–59.90 DAP). The early maturity varieties consistently required less AT10 to reach the IHT than the later maturity varieties. However, all of the varieties reached the IHT at similar SMC levels of about 35%. CONCLUSION: The later maturity varieties reached the IHT at later DAPs when they acquired more AT10 than the early maturity varieties but both reached it at similar SMC levels. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Summary: RUBylation plays essential roles in plant growth and development through regulating Cullin‐RING ubiquitin E3 ligase (CRL) activities and the CRL‐mediated protein degradations. However, the function of RUBylation in regulating kernel development remains unclear.Through genetic and molecular analyses of a small kernel 501 (smk501) mutant in maize (Zea mays), we cloned the smk501 gene, revealed its molecular function, and defined its roles in RUBylation pathway and seed development.Smk501 encodes a RUBylation activating enzyme E1 subunit ZmECR1 (E1 C‐TERMINAL RELATED 1) protein. Destruction in RUBylation by smk501 mutation resulted in less embryo and endosperm cell number and smaller kernel size. The transcriptome and proteome profiling, hormone evaluation and cell proliferation observation revealed that disturbing ZmECR1 expression mainly affects pathways on hormone signal transduction, cell cycle progression and starch accumulation during kernel development. In addition, mutant in zmaxr1 (Auxin resistant 1), another RUB E1 subunit, also showed similar defects in kernel development. Double mutation of zmecr1 and zmaxr1 lead to empty pericarp kernel phenotype.RUBylation is a novel regulatory pathway affecting maize kernel development, majorly through its functions in modifying multiple cellular progresses. [ABSTRACT FROM AUTHOR]

Leafy (Lfy1) is a typical late‐flowering mutant with locus being fine‐mapped, but its underlying molecular mechanism is unknown. In this study, two near‐isogenic lines, with and without the Lfy1 locus, were developed for phenotypic and transcriptional analysis of Lfy1‐mediated floral transition. Phenotypic observation showed that wild‐type (WT) plants transited into the tassel primordium at the V6 (6 expanded leaves) stage, whereas the Lfy1 mutant maintained the vegetative stage up to the V9 stage. Transcriptome analysis of shoot tips of both lines revealed more differentially expressed genes (DEGs) at the V5 (394) than the V3 stage (227). Functional enrichment analysis showed that circadian clock pathway genes exhibited lower expression levels in the Lfy1 mutant than in the WT at the V5 stage. A few integrator genes that functioned as downstream regulators of circadian clock genes also showed a lower transcript abundance in mutant lines, suggesting that the Lfy1‐mediated late‐flowering phenotype was partially caused by inefficient expression of circadian clock pathway genes. These results provide molecular clues for the late‐flowering phenotype of the Lfy1 mutant. [ABSTRACT FROM AUTHOR]

Genomic prediction (GP), which could predict the breeding value of crop plants genotyped with molecular markers, has been carried out in multiple species. Prediction accuracy (PA) of GP depends on various factors, including genetic relatedness and genetic basis. In this study, we examined the rationale for the low PA of GP when the training and validation populations were distinct using 170 temperate inbred lines and 210 tropical and subtropical inbred lines, respectively. All inbred lines were evaluated for 17 traits and genotyped with 550K high‐density markers. The results show that: (a) the influences of heritability and marker number on PA reflected variations in phenotypic variance captured by the genetic information; (b) the low PA of GP when the training and validation populations represent structured subpopulation is related to the ratio of subpopulation‐common alleles (RSCA) and the genetic relatedness between the two subpopulations; (c) RSCA and PA increased with the increase of genetic relatedness, suggesting that these three factors were related. Our findings would provide references when performing GP, and guidance when designing breeding populations. [ABSTRACT FROM AUTHOR]

Quantitative trait locus (QTL) mapping for seed longevity is essential for breeding modern cultivars with resistance to deterioration during postharvest storage. The inbred lines X178 and I178 showed large differences in seed vigour after artificial aging treatment, while they had similar performances in terms of most agronomic traits. An F2:3 population and a recombinant inbred line (RIL) population were generated to map QTL after 5 days under artificial aging conditions. Positive correlations were observed among all investigated traits including the aging germination rate, relative aging germination rate, aging simple vigour index, aging primary root length, aging shoot length and aging total length. Thirteen QTL were identified to locate on five chromosome regions: Chr.1:297 Mb (chromosome 1 region 297 Mb), Chr.3:205 Mb, Chr.4:240 Mb, Chr.5:205 Mb and Chr.7:155 Mb, with 2 to 4 QTL co‐located on a region. In each region, 3–8 previously identified aging‐related QTL were located, confirming the importance of these regions for controlling seed longevity in different maize populations. Taken together, the results of this work provide a foundation for further QTL fine mapping and the molecular‐assisted breeding of aging tolerant maize. [ABSTRACT FROM AUTHOR]

Maize ( Zea mays L.) root morphology exhibits a high degree of phenotypic plasticity to nitrogen (N) deficiency, but the underlying genetic architecture remains to be investigated. Using an advanced BC4F3 population, we investigated the root growth plasticity under two contrasted N levels and identified the quantitative trait loci (QTLs) with QTL-environment (Q × E) interaction effects. Principal components analysis (PCA) on changes of root traits to N deficiency (ΔLN-HN) showed that root length and biomass contributed for 45.8% in the same magnitude and direction on the first PC, while root traits scattered highly on PC2 and PC3. Hierarchical cluster analysis on traits for ΔLN-HN further assigned the BC4F3 lines into six groups, in which the special phenotypic responses to N deficiency was presented. These results revealed the complicated root plasticity of maize in response to N deficiency that can be caused by genotype-environment (G × E) interactions. Furthermore, QTL mapping using a multi-environment analysis identified 35 QTLs for root traits. Nine of these QTLs exhibited significant Q × E interaction effects. Taken together, our findings contribute to understanding the phenotypic and genotypic pattern of root plasticity to N deficiency, which will be useful for developing maize tolerance cultivars to N deficiency. [ABSTRACT FROM AUTHOR]

With 2 figures and 2 tables Abstract Plant height (PH), ear height (EH) and the PH/EH ratio have a great effect on plant lodging in maize ( Zea mays L.) under intensive cropping systems. To understand the genetic mechanisms controlling PH, EH and the PH/EH ratio in response to nitrogen (N) or phosphorus (P) supply, a set of 218 recombinant inbred lines (RILs) was used to evaluate PH, EH, PH/EH ratio and grain yield (GY) and grain yield components under low N, low P and normal N and P supply (NP). A total of 100 QTLs (quantitative trait loci) were detected for the traits investigated. Several QTLs were found to be associated with PH (bin 1.06/1.07) only, both PH and EH (umc1692 at bin 5.01/5.03; umc2313-umc1006 at bin 6.02) and the PH/EH ratio (bnlg1484-bnlg1866 at bin 1.03; umc1164-um1757 at bin 4.01) which was also associated with grain yield. N- or P-inducible QTLs for PH, EH and the PH/EH ratio were found in both years and are sensitive to weather conditions. [ABSTRACT FROM AUTHOR]