Anthocyanins are a class of antioxidants that scavenge free radicals in cells and play an important role in promoting human health and preventing many diseases. Here, we characterized a maize Bronze gene (BZ1) from the purple colored W22 introgression line, which encodes an anthocyanin 3-O-glucosyltransferase, a key enzyme in the anthocyanin synthesis pathway. Mutation of ZmBZ1 showed bronze-colored seeds and reduced anthocyanins in seeds aleurone layer, seedlings coleoptile, and stem of mature plants by comparison with purple colored W22 (WT). Furthermore, we proved that maize BZ1 is an aleurone layer-specific expressed protein and sub-located in cell nucleus. Real-time tracing of the anthocyanins in developing seeds demonstrated that the pigment was visible from 16 DAP (day after pollination) in field condition, and first deposited in the crown part then spread all over the seed. Additionally, it was transferred along with the embryo cell activity during seed germination, from aleurone layer to cotyledon and coleoptile, as confirmed by microscopy and real-time qRT-PCR. Finally, we demonstrated that the ZmBZ1 contributes to stress tolerance, especially salinity. Further study proved that ZmBZ1 participates in reactive oxygen scavenging (ROS) by accumulating anthocyanins, thereby enhancing the tolerance to abiotic stress.

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 F_2:3 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.

Typically, sweet corn, particularly sh2 sweet corn, has low seed vigor owing to its high sugar and low starch content, which is a major problem in sweet corn production, particularly at low temperatures. There is considerable variation in the germination rates among sweet corn varieties under low-temperature conditions, and the underlying mechanisms behind this phenomenon remain unclear. In this study, we screened two inbred sweet corn lines (tolerant line L282 and sensitive line L693) differing in their low-temperature germination rates; while no difference was observed in their germination rates at normal temperatures. To identify the specifically induced genes influencing the germination capacity of sweet corn at low temperatures, a transcriptome analysis of the two lines was conducted at both normal and low temperatures. Compared to the lines at a normal temperature, 3926 and 1404 differently expressed genes (DEGs) were identified from L282 and L693, respectively, under low-temperature conditions. Of them, 830 DEGs were common DEGs (cDEGs) that were identified from both L282 and L693, which were majorly enriched in terms of microtubule-based processes, histone H3-K9 modification, single-organism cellular processes, and carbohydrate metabolic processes. In addition, 3096 special DEGs (sDEGs), with 2199 upregulated and 897 downregulated, were detected in the tolerant line L282, but not in the sensitive line L693. These sDEGs were primarily related to plasma membranes and oxygen-containing compounds. Furthermore, electric conductivity measurements demonstrated that the membrane of L282 experienced less damage, which is consistent with its strong tolerance at low temperatures. These results expand our understanding of the complex mechanisms involved in the cold germination of sweet corn and provide a set of candidate genes for further genetic analysis.

As soybean plays an indispensable role in the supply of vegetable oil and protein, balancing the relationship between seed quality and yield traits according to human demand has become an important breeding goal for soybean improvement. Here, 256 intraspecific recombinant inbred lines (RILs), derived from a cross between Qi Huang No.34 (QH34) and Ji Dou No.17 (JD17), were used for quantitative trait loci (QTLs) mapping with remarkable four chemical and physical properties with a purpose for exploring the distribution of excellent alleles in germplasm resources in China. A total of 25 QTLs were detected, of which 10 QTLs inherited the alleles from the parent QH34. Pedigree research on favorable alleles on these QTLs showed the process of excellent alleles pyramided into QH34. Meta-analysis of the 25 QTLs by comparing with existed QTLs in previous study identified 17 novel QTLs. QTLs with pleiotropic effects have been detected. Furthermore, three representative elite recombinant inbred lines in different locations that have great potential in soybean breeding were selected, and finally, four seed weight-related candidate genes were identified. The discovery of these QTLs provides a new guidance for combining the diversity and rarity of germplasm resources, which can effectively increase population genetic diversity and broaden genetic basis of varieties.

Maize originated from tropical regions and is extremely sensitive to low temperature during germination. Our previous work identified a major QTL, qp1ER1-1, for low temperature germination ability (LTGA) of maize. Here, we introgressed qp1ER1-1 from the tolerant line L220 into the sensitive line PH4CV to generate two near isogenic lines NIL^220-3 and NIL^220-25. When germinated under cold temperature for 25 days (Cold-25), the NILs showed similar seedling root length and shoot length to L220, but significantly higher than PH4CV. However, when germinated under cold temperature for 15 days (Cold-15) or under normal temperature (25 °C) for 3 days (CK-3), all lines showed similar seedling performance, indicating that introgression of qp1ER1-1 from L220 into PH4CV could improve LTGA of NIL^220-3 and NIL^220-25. The whole seedlings, including root and shoot, of Cold-15 and CK-3 were harvested for transcriptome analysis, when both stayed at a similar developmental stage. Dry seed embryo was sequenced as a non-germination control (CK-0). Compared with PH4CV, the tolerant line (L220, NIL^220-3, and NIL^220-25) specifically expressed genes (different expressed genes, DEGs) were identified for CK-0, Cold-15, and CK-3. Then, DEGs identified from Cold-15, but not from CK-0 or CK-3, were defined as tolerant line specifically expressed LTGA genes. Finally, 1786, 174, and 133 DEGs were identified as L220, NIL^220-3, and NIL^220-25 specifically expressed LTGA genes, respectively. Of them, 27 were common LTGA genes that could be identified from all three tolerant lines, with two (Zm00001d031209 and Zm00001d031292) locating in the confidence interval of qp1ER1-1. In addition, GO analysis revealed that L220 specifically expressed LTGA genes were majorly enriched in the cell division process and plasma membrane related categories. Taken together, these results provided new insight into the molecular mechanism of maize seed LTGA and facilitated the cloning of the qp1ER1-1 gene.

Anthocyanin, a kind of flavonoid, plays a crucial role in plant resistance to abiotic stress. Salt stress is a kind of abiotic stress that can damage the growth and development of plant seedlings. However, limited research has been conducted on the involvement of maize seedlings in salt stress resistance via anthocyanin accumulation, and its potential molecular mechanism is still unclear. Therefore, it is of great significance for the normal growth and development of maize seedlings to explore the potential molecular mechanism of anthocyanin improving salt tolerance of seedlings via transcriptome analysis. In this study, we identified two W22 inbred lines (tolerant line pur–W22 and sensitive line bro–W22) exhibiting differential tolerance to salt stress during seedling growth and development but showing no significant differences in seedling characteristics under non–treatment conditions. In order to identify the specific genes involved in seedlings’ salt stress response, we generated two recombinant inbred lines (RIL^pur–W22 and RIL^bro–W22) by crossing pur–W22 and bro–W22, and then performed transcriptome analysis on seedlings grown under both non–treatment and salt treatment conditions. A total of 6100 and 5710 differentially expressed genes (DEGs) were identified in RIL^pur–W22 and RIL^bro–W22 seedlings, respectively, under salt–stressed conditions when compared to the non–treated groups. Among these DEGs, 3160 were identified as being present in both RIL^pur–W22 and RIL^bro–W22, and these served as commonly stressed EDGs that were mainly enriched in the redox process, the monomer metabolic process, catalytic activity, the plasma membrane, and metabolic process regulation. Furthermore, we detected 1728 specific DEGs in the salt–tolerant RIL^pur–W22 line that were not detected in the salt–sensitive RIL^bro–W22 line, of which 887 were upregulated and 841 were downregulated. These DEGs are primarily associated with redox processes, biological regulation, and the plasma membrane. Notably, the anthocyanin synthesis related genes in RIL^pur–W22 were strongly induced under salt treatment conditions, which was consistented with the salt tolerance phenotype of its seedlings. In summary, the results of the transcriptome analysis not only expanded our understanding of the complex molecular mechanism of anthocyanin in improving the salt tolerance of maize seedlings, but also, the DEGs specifically expressed in the salt–tolerant line (RIL^pur–W22) provided candidate genes for further genetic analysis.