The yield of maize (Zea mays L.) is affected by the plant architecture which is associated with the distribution of light within canopy and utilization of solar energy within population. Plant architecture of maize is mainly characterized by leaf angle (LA) and leaf space (LS). To analyze the genetic mechanism of LA and LS above ear position in maize, a genetic linkage map composed of 212 simple sequence repeat markers was constructed based on a F 2 population derived from the cross between the compact inbred line CY5 and the expanded inbred line YL106. The map spanned 1,153.39 cM in length with an average interval of 5.44 cM. By using the inclusive composite interval mapping method, QTLs for LA and LS above ear position were identified based on two field mapping populations consisted of 144 F 2:3 families in three environments and 144 F 4 families, respectively. In F 2:3 population, three consistent QTLs qSecLA1a, qThiLA1a, and qThiLS7 were detected in both single-environment analysis and joint-environment analysis. The qSecLA1a between bnlg1803 and bnlg1007 on chromosome 1.02 explained 26.99 and 18.51 % of the phenotypic variation, qThiLA1a between bnlg1803 and bnlg1007 on chromosome 1.02 explained 24.14 and 22.00 % of the phenotypic variation and qThiLS7 between bnlg1305 and umc1787 on chromosome 7.02/7.03 explained 13.77 and 9.96 % of the phenotypic variation in single environment analysis while the three QTLs explained 29.10, 31.86 and 11.20 % of the phenotypic variation, respectively in joint environment analysis. Moreover, there were major QTLs near bnlg1803 on chromosome 1 for SecLA and ThiLA stably expressing in F 2:3 and F 4 generations. The results of this study could provide references for genetic modification and molecular marker-assisted selection for LA and LS in maize.

Elucidating the correlations among maize (Zea mays L.) brace‐root traits and identifying the quantitative trait loci (QTL) that control the traits are important for genetic improvement of brace‐root traits. Two maize inbred lines, Yi17 (well‐developed root system) and Yi16 (poorly developed root system), an F2 population derived from their cross containing 276 individuals, and an F2:3 population containing 241 families were used to analyze the correlations among brace‐root traits and determine the QTL for brace‐root traits at Xiema and Hechuan in 2014 and 2015. All brace‐root traits were highly significantly correlated with each other. In particular, brace‐root diameter was highly correlated with brace‐root fresh weight (r = 0.730), brace‐root dry weight (r = 0.729), root fresh weight (r = 0.734), and root dry weight (r = 0.754). A total of 212 simple sequence repeat (SSR) markers were used to develop a genetic map based on the F2 population. The total length of the genetic map was 1558.9 cM, with a mean interval of 7.35 cM between adjacent markers. Ninety‐three QTL controlling the brace‐root traits were detected in generations F2 at Xiema in 2014 and F2:3 at Xiema and Hechuan in 2015. However, only two consistent major QTL were identified in F2:3 generation—qBRTN8b for brace‐root tier number and qBRD8b for brace‐root diameter. The qBRTN8b was located in the mmc0181 to bnlg1031 interval (bin 8.06) on chromosome 8, which explained 32.64% (at Xiema) and 16.18% (at Hechuan) of phenotypic variation. The qBRD8b was mapped in the umc2367 to umc1846 interval (bin 8.05) on chromosome 8, which explained 14.28% (at Xiema) and 10.41% (at Hechuan) of phenotypic variation. Moreover, three new important chromosomal regions harboring QTL for brace‐root traits were detected—bins 5.04, 6.06, and 8.05 to 8.06. These results could provide a very important reference for evaluating root traits under field conditions and for fine mapping QTL of brace‐root traits in maize.

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Gene imprinting describes an epigenetic phenomenon, whereby genetically identical alleles are differentially expressed dependent on parent-of-origin. Some imprinted genes belonged to NUCLEAR FACTOR Y (NF-Y) transcription factors, which were involved in many important metabolic processes in plant. The characterizations of imprinted genes are of great importance for their function exploration. In this paper, 15 non-redundant NF-YC genes were identified in the maize genome and the paternally expressed gene NF-YC8 was further analyzed. NF-YC8 primarily expressed in maize immature ear and tassel and phylogenetic analysis showed that NF-YC8 was highly homologous with Arabidopsis thaliana NF-YC2 genes which function in regulation of the flowering processes, ER stress response. Furthermore, NF-YC8 was a differential, gene-specific imprinted gene at 14 DAP and persistently imprinted throughout later endosperm development in the B73/Mo17 genetic background. Bisulfite sequencing for NF-YC8 in maize endosperm showed that the paternal alleles were higher methylated (CG, CHG and CHH contexts) than maternal alleles in the 5' upstream region, and the coding region was highly methylated in CG context. Additionally, TE (CG, CHG and CHH contexts) and repetitive region (CG and CHG contexts) were all highly methylated. These results are the first description of evolution and molecular characterization of maize NF-YC8 and will provide new references for maize NF-YC genetic analysis.

Leaf senescence plays an important role in the improvement of maize kernel yields. However, the underlying regulatory mechanisms of leaf senescence in maize are largely unknown. We isolated ZmVQ52 and studied the function of ZmVQ52 which encoded, a VQ family transcription factor. ZmVQ52 is constitutively expressed in maize tissues, and mainly expressed in the leaf; it is located in the nucleus of maize protoplasts. Four WRKY family proteins—ZmWRKY20, ZmWRKY36, ZmWRKY50, and ZmWRKY71—were identified as interacting with ZmVQ52 . The overexpression of ZmVQ52 in Arabidopsis accelerated premature leaf senescence. The leaf of the ZmVQ52 -overexpression line showed a lower chlorophyll content and higher senescence rate than the WT. A number of leaf senescence regulating genes were up-regulated in the ZmVQ52 -overexpression line. Additionally, hormone treatments revealed that the leaf of the ZmVQ52 -overexpressed line was more sensitive to salicylic acid (SA) and jasmonic acid (JA), and had an enhanced tolerance to abscisic acid (ABA). Moreover, a transcriptome analysis of the ZmVQ52 -overexpression line revealed that ZmVQ52 is mainly involved in the circadian pathway and photosynthetic pathways.