RNA m6A modification facilitates DNA methylation during maize kernel development.

N6-methyladenosine (m6A) in mRNA and 5-methylcytosine (5mC) in DNA have critical functions for regulating gene expression and modulating plant growth and development. However, the interplay between m6A and 5mC is an elusive territory and remains unclear mechanistically in plants. We reported an occurrence of crosstalk between m6A and 5mC in maize (Zea mays) via the interaction between mRNA adenosine methylase (ZmMTA), the core component of the m6A methyltransferase complex, and decrease in DNA methylation 1 (ZmDDM1), a key chromatin-remodeling factor that regulates DNA methylation. Genes with m6A modification were coordinated with a much higher level of DNA methylation than genes without m6A modification. Dysfunction of ZmMTA caused severe arrest during maize embryogenesis and endosperm development, leading to a significant decrease in CHH methylation in the 5' region of m6A-modified genes. Instead, loss of function of ZmDDM1 had no noteworthy effects on ZmMTA-related activity. This study establishes a direct link between m6A and 5mC during maize kernel development and provides insights into the interplay between RNA modification and DNA methylation.

The RHW1-ZCN4 regulatory pathway confers natural variation of husk leaf width in maize.

Maize husk leaf - the outer leafy layers covering the ear - modulates kernel yield and quality. Despite its importance, however, the genetic controls underlying husk leaf development remain elusive. Our previous genome-wide association study identified a single nucleotide polymorphism located in the gene RHW1 (Regulator of Husk leaf Width) that is significantly associated with husk leaf-width diversity in maize. Here, we further demonstrate that a polymorphic 18-bp InDel (insertion/deletion) variant in the 3' untranslated region of RHW1 alters its protein abundance and accounts for husk leaf width variation. RHW1 encodes a putative MYB-like transcriptional repressor. Disruption of RHW1 altered cell proliferation and resulted in a narrower husk leaf, whereas RHW1 overexpression yielded a wider husk leaf. RHW1 positively regulated the expression of ZCN4, a well-known TFL1-like protein involved in maize ear development. Dysfunction of ZCN4 reduced husk leaf width even in the context of RHW1 overexpression. The InDel variant in RHW1 is subject to selection and is associated with maize husk leaf adaption from tropical to temperate regions. Overall, our results identify that RHW1-ZCN4 regulates a pathway conferring husk leaf width variation at a very early stage of husk leaf development in maize.

Detection of urban hidden faults using group-velocity ambient noise tomography beneath Zhenjiang area, China.

The Mufushan-Jiaoshan fault (MJF) is a hidden active fault located on the north side of the Ningzhen Mountain Range and developed along the Yangtze River in Zhenjiang area, China. In this paper, the structure of MJF is detected and studied using group-velocity ambient noise tomography. In the study area (18 km × 25 km), 47 short-period seismic stations were deployed with the average station spacing of about 3 km and 24 days (from 27 February to 22 March 2019) of continuous ambient-noise recordings were collected. And 510 group velocity dispersion curves in the period band 0.5-5 s were extracted using the vertical component data. And then the three-dimensional shear-wave velocity structure was inverted using group dispersion data by the direct surface-wave tomographic method. Our results are consistent with the geological background of the study area, showing that in the depth range of 0.6-1.5 km, the north side of MJF presents a relatively high velocity, and the south side presents a distribution pattern of high and low velocity. While in the depth range of 1.5-2.0 km, the shear-wave velocity (Vs) model is relatively simple with relatively low velocity on the north side and relatively high velocity on the south side. And the gradient zone of Vs may be the location of the main fracture surface of MJF. The good correspondence between the Vs model and the fault structure indicates that the ambient noise tomography method can be used as an effective method for detecting hidden faults in urban environments.