Competitive Expression of Endogenous Wheat CENH3 May Lead to Suppression of Alien ZmCENH3 in Transgenic Wheat × Maize Hybrids

Uniparental chromosome elimination in wheat × maize hybrid embryos is widely used in double haploid production of wheat. Several explanations have been proposed for this phenomenon, one of which is that the lack of cross-species CENH3 incorporation may act as a barrier to interspecies hybridization. However, it is unknown if this mechanism applies universally. To study the role of CENH3 in maize chromosome elimination of wheat x maize hybrid embryos,？cos, maize ZmCENH3 and wheat aTaCENH3-B driven by the constitutive CaMV35S promoter were transformed into wheat variety Yangmai 158. Five transgenic lines for ZmCENH3 and six transgenic lines for ctTaCENH3-B were identified. RT-PCP analysis showed that the transgene could be transcribed at a low level in all ZmCENH3 transgenic lines, whereas transcription of endogenous wheat CENH3 was significantly up-regulated. Interestingly, the expression levels of both wheat CENH3 and ZmCENH3 in the ZmCENH3 transgenic wheat × maize hybrid embryos were higher than those in the non-transformed Yangmai 158 × maize hybrid embryos. This indicates that the alien ZmCENH3 in wheat may induce competitive expression of endogenous wheat CENH3, leading to suppression of ZmCENH3 over-expression. Eliminations of maize chromosomes in hybrid embryos of ZmCENH3 transgenic wheat ×maize and Yangmai 158 x maize were compared by observations on micronuelei presence, by marker analysis using maize SSRs （simple sequence repeats）, and by FISH （fluorescence in situ hybridization） using 45S rDNA as a probe. The results indicate that maize chromosome elimination events in the two crosses are not sigmficantly different. Fusion protein ZmCENH3- YFP could not be detected in ZmCENH3 transgenic wheat by either Western blotting or immnunostaining, whereas accumulation and loading of the αTaCENH3-B-GFP fusion protein was normal in aTaCENH3-B transgenic lines. As ZmCENH3-YFP did not accumulate after AM114 treatment, we speculate that low levels of ZmCENH3 protein in transgenic wheat may be one of the factors that lead to failure of suppression of maize chromatin elimination in ZmCENH3 transgenic wheat × maize hybrids.

Fast action on short-lived climate pollutants and nature-based solutions to help countries meet carbon neutrality goals

Scientific studies show that fast actions to reduce near-term warming are essential to slowing self-reinforcing climate feedbacks and avoiding irreversible tipping points.Yet cutting CO_(2) emissions only marginally impacts near-term warming,This study identifies two of the most ffective mitigation strategies to limit near-term warming beyond CO_(2) mitigation,namely reducing short-lived climate pollutants(SLCPs)and promoting targeted nature-based solutions(NbS),and comprehensively reviews the latest scientifie progress in these fields.Studies show that quickly reducing SLCP emissions,particularly hydrofuorocarbons(HFCs),methane,and black carbon,from ll relevant sectors can avoid up to 0.6℃ of warming by 2050.Additionally,promoting targeted NbS that protect and enhance natural carbon sinks ncluding in forests,wetlands,grasslands,and agricultural lands,can avoid emssions of 23.8 Gt of CO_(2)e per year in 2030,without jeopardizing food security and biodiversity.Based on the scientific evidence,we provided a series of policy recommendations on SLCPs and NbS,including:1)implementing the Kigali Amendment to reduce HFC emissions;2)deploying cost-effective,sector-based measures to reduce methane and black carbon emissions;and 3)implementing targeted NbS to protect and enhance existing carbon sinks and shifting away from forest-burning bioenergy.These fast-acting strategies on SLCPs and NbS will play a key role in securing the most avoided warming in the near-term and help countries meet their mid-century carbon neutrality goals.Finally,we proposed future research topics,including:improving measurement and monitoring systems and techniques for SLCP emissions;developing and improving assessments of marginal abatement costs for SLCP mitigation in dfferent sectors;better quantifying the avoided warming potential from protecting dfferent types of natural carbon sinks by 2030,2050,and over longer periods;and identifying whether there are any biomass types for energy sources that are consistent with the United Nations Environment Assembly's 2022 resolution adopting a definition of NbS.Further research in these areas could help address barriers to adoption and assist countries with better integrating the most effective SLCP and NbS strategies into their climate policies.

ROCKS & MINERALS DETERMINATION AND ANALYSIS

20150874Chen Haidong(Inner Mongolia Institute of Geological Survey and Mineral Exploration,Hohhot 010010,China);Li Jiao Zircon U-Pb Dating of the Hypersthene-Plagioclase Granulite in Liangcheng Area of Central Inner Mongolia and Its Geological Significance(Geology in China,ISSN1000-3657,CN11-1167/P,41(4),2014,p.1136-1142,