New Exploration On The Mechanism Of Maize Seed Germination Under Salt Stress

Maize is one of the most widely cultivated food crops in China and the world,and it is planted less than wheat and rice.Maize is very important for our life.The germination of maize seeds is related to the increase of maize yield.This is a biological process regulated by various factors.Through seed germination,the radicle of mature seeds can begin to penetrate the seed coat Germination grows into seedlings.There are many factors that affect the germination of maize seeds,including plant hormones,environmental stresses such as salt stress,and so on.The effect of salt stress on the germination of maize seeds is the focus of this experimental study.The area of saline-alkali land in China is nearly 100 million hectares,most of which are distributed in northern areas,and are highly coincident with China's maize producing areas.The study of the response of maize seeds to salt stress during germination will help increase the yield of the main maize producing areas in northern China.There are great differences in seed morphology between monocotyledons and dicotyledons.Monocotyledons have thick endosperm layer to wrap the embryo,but there is no endosperm layer in mature dicotyledons.Therefore,the research results of Arabidopsis as a model plant cannot be completely used for reference by maize research.Therefore,we selected maize as the material to study the function and mutual regulation mechanism of endosperm and embryo during germination,especially under germination.We studied the regulation mechanism of maize germination under NaCl stress through a series of physiological and biochemical,molecular biology,and bioinformatics methods.We get the following results:(1)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.(2)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.(3)By using advanced profiling techniques such as RNA sequencing and SWATH-MSbased 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.(4)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.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.