The HuangZaoSi Maize Genome Provides Insights into Genomic Variation and Improvement History of Maize

Maize is a globally important crop that was a classic model plant for genetic studies. Here, we report a 2.2 Gb draft genome sequence of an elite maize line, HuangZaoSi (HZS). Hybrids bred from HZS-improved lines (HILs) are planted in more than 60% of maize fields in China. Proteome clustering of six completed sequeneed maize genomes show that 638 proteins fall into 264 HZS-specific gene families with the majority of contributions from tandem duplication events. Resequencing and comparative analysis of 40 HZSrelated lines reveals the breeding history of HILs. More than 60% of identified selective sweeps were clustered in identity.by.descent conserved regions, and yield-related genes/QTLs were enriched in HZS characteristic selected regions. Furthermore, we dem on strated that HZS-specific family genes were not uniformly distributed in the genome but enriched in improvement/function.related genomic regions. This study provides an important and novel resource for maize genome research and expands our knowledge on the breadth of genomic variation and improvement history of maize.

Visualizing DC morphology and T cell motility to characterize DC-T cell encounters in mouse lymph nodes under mTOR inhibition

Mammalian target of rapamycin(mTOR),a serine/threonine kinase orchestrating cellular metabolism,is a crucial immune system regulator.However,it remains unclear how mTOR regulates dendritic cell(DC) function in vivo,especially DC-T cell encounters,a critical step for initiating adaptive immune responses.We dynamically visualized DC-T contacts in mouse lymph node using confocal microscopy and established an encounter model to characterize the effect of mTOR inhibition on DC-T cell encounters using DC morphology.Quantitative data showed mTOR inhibition via rapamycin altered DC shape,with an increased form factor(30.17%) and decreased cellular surface area(20.36%) and perimeter(22.43%),which were associated with Cdc42 protein downregulation(52.71%).Additionally,DCs adopted a similar morphological change with Cdc42 inhibition via ZCL278 as that observed with mTOR inhibition.These morphologically altered DCs displayed low encounter rates with T cells.Time-lapse imaging data of T cell motility supported the simulated result of the encounter model,where antigen-specific T cells appeared to reduce arrest in the lymph nodes of rapamycin-pretreated mice relative to the untreated group.Therefore,mTOR inhibition altered DC morphology in vivo and decreased the DC-T cell encounter rate,as well as Cdc42 inhibition.By establishing an encounter model,our study provides an intuitive approach for the early prediction of DC function through morphological quantification of form factor and area.