Pengfei Leng

Flowering time, plays a crucial role in tobacco ecological adaptation besides its substantial influence on tobacco production and leaf quality. Meanwhile, it is sensitive to biotic or abiotic challenges. The plant hormones Gibberellins (GAs), controlling a number of metabolic processes, govern plants growth and development. In this study, we created a late flowering mutant HG14 through knocking out NtGA3ox1 by CRISPR/Cas9. It took around 13.0 and 12.1 days longer to budding and flowering compared to wild type Honghuadajinyuan. Nearly all of the evaluated agronomic characters deteriorated in HG14, showing slower growth and noticeably shorter and narrower leaves. We found that NtGA3ox was more prevalent in flowers through quantitative reverse transcription PCR analysis. Transcriptome profiling detected 4449, 2147, and 4567 differently expressed genes at the budding, flowering, and mature stages, respectively. The KEGG pathway enrichment analysis identified the plant-pathogen interaction, plant hormone signal transduction pathway, and MAPK signaling pathway are the major clusters controlled by NtGA3ox1 throughout the budding and flowering stages. Together with the abovementioned signaling pathway, biosynthesis of monobactam, metabolism of carbon, pentose, starch, and sucrose were enriched at the mature stage. Interestingly, 108 up- and 73 down- regulated DEGs, impairing sugar metabolism, diterpenoid biosynthesis, linoleic and alpha-linolenic acid metabolism pathway, were continuously detected accompanied with the development of HG14. This was further evidenced by the decreasing content of GA metabolites such as GA4 and GA7, routine chemicals, alkaloids, amino acids, and organic acids Therefore, we discovered a novel tobacco flowering time gene NtGA3ox1 and resolved its regulatory network, which will be beneficial to the improvement of tobacco varieties.

Variation in flowering plays a major role in maize photoperiod adaptation during long-term domestication. It is of high value to investigate the genetic basis of maize flowering under a wide range of environmental conditions in order to overcome photoperiod sensitivity or enhance stress tolerance. A recombinant inbred line (RIL) population derived from a cross between Huangzaosi and Mo17, composed of 121 lines and genotyped by 8329 specifically developed markers, was field evaluated in two consecutive years under two planting densities (67,500 and 120,000 plants ha⁻¹) and two water treatments (normal irrigation and drought stress at the flowering stage). The days to silking (DTS), days to anthesis (DTA), and anthesis to silking interval (ASI) were all evaluated. Within the RIL population, DTS and DTA expanded as planting density and water deficit increased. For DTA, DTS, ASI, and ASI-delay, a total of 22, 17, 21, and 11 QTLs were identified, respectively. More than two significant QTLs were identified in each of the nine chromosomal intervals. Under diverse conditions and locations, six QTLs (quantitative trait locus) for DTS and DTA were discovered in Chr. 8: 118.13–125.31 Mb. Three chromosome regions, Chr. 3: 196.14–199.89 Mb, Chr. 8: 169.02–172.46 Mb, and Chr. 9: 128.12–137.26 Mb, all had QTLs for ASI-delay under normal and stress conditions, suggesting their possible roles in stress tolerance enhancement. These QTL hotspots will promote early-maturing or multiple abiotic stress-tolerant maize breeding, as well as shed light on the development of maize varieties with a broad range of adaptations.

Drought is one of the most critical environmental factors constraining maize production. When it occurs at the flowering stage, serious yield losses are caused, and often, the damage is irretrievable. In this study, anthesis to silk interval (ASI), plant height (PH), and ear biomass at the silking date (EBM) of 279 inbred lines were studied under both water-stress (WS) and well-water (WW) field conditions, for three consecutive years. Averagely, ASI was extended by 25.96%, EBM was decreased by 17.54%, and the PH was reduced by 12.47% under drought stress. Genome-wide association studies were carried out using phenotypic values under WS, WW, and drought-tolerance index (WS-WW or WS/WW) and applying a mixed linear model that controls both population structure and relative kinship. In total, 71, 159, and 21 SNPs, located in 32, 59, and 12 genes, were significantly (P < 10⁻⁵) associated with ASI, EBM, and PH, respectively. Only a few overlapped candidate genes were found to be associated with the same drought-related traits under different environments, for example, ARABIDILLO 1, glycoprotein, Tic22-like, and zinc-finger family protein for ASI; 26S proteasome non-ATPase and pyridoxal phosphate transferase for EBM; 11-ß-hydroxysteroid dehydrogenase, uncharacterised, Leu-rich repeat protein kinase, and SF16 protein for PH. Furthermore, most candidate genes were revealed to be drought-responsive in an association panel. Meanwhile, the favourable alleles/key variations were identified with a haplotype analysis. These candidate genes and their key variations provide insight into the genetic basis of drought tolerance, especially for the female inflorescence, and will facilitate drought-tolerant maize breeding.

Drought is one of the most critical environmental factors constraining corn production especially when it occurs during flowering, resulting in serious yield losses. In this study, anthesis to silk interval (ASI), plant height (PH), and ear biomass at the silking date (EBM) of 279 inbred lines were evaluated under water-stress (WS) and well-water (WW) field conditions for three consecutive years. Averagely, ASI was extended by 25.96%, ear biomass was decreased by 17.54%, and the PH was reduced by 12.47% under drought stress conditions. Genome wide association studies (GWAS) were carried out using phenotypic values under WS, WW and drought-tolerance index (WS-WW or WS/WW) applying mixed linear model controlling both population structure and relative kinship. Totally, 71, 159, and 21 SNPs were significantly (P < 10^-5) associated with ASI, ear biomass, and PH, respectively. Candidate genes encoding ARABIDILLO 1 protein, glycoprotein, Tic22-like and Zinc finger family protein for ASI, and 26S proteasome non-ATPase regulatory subunit-9 for EBM, were identified under both WW and WS conditions. Pyridoxal phosphate transferase was associated with EBM under drought stress treatment in consecutive two years. Furthermore, most candidate genes were evidenced to be drought responsive in the association panel. Meanwhile, the favourable/drought tolerance haplotypes were identified based on haplotype analysis. These findings provide insights into the genetic basis of drought tolerance at the flowering stage especially for the female inflorescence development and will facilitate high drought tolerant maize breeding.

Here, we reviewed major transcription factors of maize that confer drought stress tolerance, and their target genes and involved signaling pathway. Transcription factors in maize can be promising candidates for improving comprehensive resistance of multiple environmental stimuli.

Improving maize starch content is of great importance for both forage and grain yield. In this study, 13 starch degradability traits were analysed including percentage of the seedling area, floury endosperm, hard endosperm of total grain area, percentage of the floury endosperm surface and vitreousness ratio surface hard: floury endosperm surface, etc. We mapped quantitative trait loci (QTL) in a biparental population of 309 doubled haploid lines based on field phenotyping at two locations. A genetic linkage map was constructed using 168 SSR (simple sequence repeat) markers, which covered 1508 cM of the maize genome, with an average distance of 9.0 cM. Close phenotypic and genotypic correlations were found for all traits, and were all statistically significant (p = 0.01) at two locations. Major QTL for more than two traits were detected, especially in two regions in bins 4.05–4.06 and 7.04–7.05, associated with 13 and 9 traits, respectively. This study contributes to marker‐assisted breeding and also to fine mapping candidate genes associated with maize starch degradability.

Four agronomic traits were analysed including dry matter concentration (DMC) and dry matter yield (DMY) for stover, plant height (PHT) and days from planting to silking (DPS). We mapped quantitative trait loci (QTL) in three populations with doubled haploid lines (DHL), one RIL population and two testcross (TC) populations derived from crosses between two of the four populations mentioned above to elite tester lines, based on field phenotyping at multiple locations and years for each; 146–168 SSRs were used for genotyping of the four mapping populations. Significant high phenotypic and genotypic correlations were found for all traits at two locations, while DMC was negatively correlated with the other traits. A total of 42, 41, 54, and 45 QTL were identified for DMC, DMY, PHT, and DPS, respectively, with 9, 7, 12, and 7 major QTL for each trait. Most detected QTL displayed significant interactions with environment. Major QTL detected in more than two populations will contribute to marker‐assisted breeding and also to fine mapping candidate genes associated with maize agronomic traits.

Four forage maize stover quality traits were analysed including in vitro digestibility of organic matter (IVDOM), neutral detergent fibre (NDF), water‐soluble carbohydrates (WSC) and digestibility of NDF (DNDF). We mapped quantitative trait loci (QTL) in three DH (doubled haploid) populations (totally 250–720 DH lines): one RIL population (358 lines) and two testcross (TC) populations, based on field phenotyping at multiple locations and years for each. High phenotypic and genotypic correlations were found for all traits and significant (p < .01) at two locations, and NDF was negatively correlated with the other traits. QTL analyses were conducted by composite interval mapping. A total of 33, 23, 32 and 25 QTL were identified for IVDOM, NDF, WSC and DNDF, respectively, with three, four, five and two major QTL for each. Few consistent QTL for IVDOM, WSC and DNDF were detected in more than two populations. This study contributed to the identification of key QTL associated with forage maize digestibility traits and is beneficial for marker‐assisted breeding and fine mapping of candidate genes associated with forage maize quality.