Zea mays cultivar:B73 Raw sequence reads. Zea mays cultivar:B73

Germination is a highly variable biological process by which radicle of mature seeds start to penetrate surrounding barriers for seedling establishment. However, little is known how high salinity affects seed germination of C4 plant, Zea mays. To this end, an integrative large-scale profiling experiment has been performed in combination with traditional physiological and molecular analysis on germinating maize seeds in response to sodium chloride treatment. Our initial germination assay suggested that isolated embryo alone was able to germinate under 200 mM NaCl treatment, whereas the intact seeds were highly repressed. Thus, we hypothesized that maize endosperm may function in sensation and transduction of salt signal to surrounding tissues such as embryo, showing a completely different responsive model from that of Arabidopsis. Furthermore, we analysed in vivo ABA distribution and quantity by modified immunofluorescence method. The result demonstrated that ABA level in isolated embryo under NaCl treatment failed to increase by comparing with the water control, suggesting the elevation of ABA level is an endosperm dependent process. Subsequently, by using advanced profiling techniques such as RNA sequencing and SWATH-MS-based quantitative proteomics, we found that substantial post-transcriptional and translational changes were identified between salt-treated embryo and endosperm, suggesting that these regulatory mechanisms are pivotal short-term salt responsive strategies during maize germination. Furthermore, master regulatory proteins including splicing factors (SFs) and transcription factors (TFs) were summarized. Surprisingly, over 200 SFs and TFs were found to undergo substantial post-transcriptional modification. In particular, tens of splicing factors were shown altered protein abundance in response to salt treatment. Among 12 shared SFs between embryo and endosperm dataset, 11 of them showed contrasting expression levels under salt treatment, serving as valuable targets for further functional study. In summary, our results indicate that alternative splicing and its controlling factors (e.g. SFs) are likely to mediate early responses to salt stress during maize seed germination. However, the underlying components for signal sensing and transduction between embryo and endosperm remain to be elucidated.