| Proso millet (Panicum miliaceum L) which originated from China is one of the earliest cultivated grain.Its history of cultivation are as many as 8,000 years and it is an important grain crops in the northern area of our country. As the global shortage of water resources is increasingly serious, drought has become an important factor in agricultural development. As C4 plant, proso millet has characteristics of drought resistance and barren tolerance. It not only has rich plant genetic resources, but also can improve the drought tolerance of quality crop species. Studying a variety of physiological and biochemical reactions and molecular mechanisms of proso millet can provide theoretical basis for staple crops to improve drought resistance.Through preliminary excavation of millet transcriptome data,we find a partial sequence that is similar with NCED gene. Then we determine the sequence characteristics and have a expression analysis under drought stress:(1) Based on RT-PCR and TA cloning technology,we cloned a cDNA sequence containing a complete ORF, named for PmNCED; (2) We used Blastp, MEGA and other softwares for sequence alignment analysis of PmNCED gene and construct the phylogenetic tree. Phylogenetic tree analysis showed that, as the same category,proso millet and millet both belong to monocots grasses, and consistent with the plant taxonomy phylogenetic; (3) We used SOPMA tools to predict the secondary structure of the protein which encoded by PmNCED. Finding that the PmNCED protein constituted by 24.53% of a-helix, 28.97% of extended strand,11.45% of P-corner and 35.05% of irregular curl; (4) Using SWISS-MODEL to predict the 3D structure of PmNCED protein.We used PEG stress to treat trefoil stage of two prosomillet varieties, measuring and analyze soluble sugar, free proline, malondialdehyde (MDA) and relative water content of physiological indicators in leaves which has stressed for 8h. The results showed that:the soluble sugar content, free proline content and relative water content in ’HMZ’(No.20) are higher than the ’ZY’(No.60), and the accumulation of MDA are far less than ’ZY’;It is inferred that yellow milletl is a resistant variety for PEG stresss,’HMZ’ is a sensitive variety for PEG stress.We used the paraffin sections to observe the changes of the trefoil stage structure in prosomillet which at different times after PEG stress treatments. The results show that:with the increase of PEG stress time, the volume of the leaf epidermal cells was significantly smaller due to water loss. Because of water loss,leaf vesicular cells had a change that from the normal swell state gradually stretched into a long strip shape, so that leaves curl upwards, thereby reducing transpiration area, reducing transpiration intensity, showed that vesicular cells associated with high drought resistance of prosomillet in seedling stage.Based on PEG stress and real-time PCR technique,we had a relative quantitative analysis of PmNCED gene in leaves. The results show:PmNCED gene is expressed in the’HMZ’and’ZY’in leaves, and the expression has continued to rise with the increasing of the PEG stress time. The relative expression become the highest at 8h in the’HMZ’. as 16 times of the control; the relative expression become the highest at 8h in the ’ZY’, as 13 times of the control. Showed that PmNCED gene was strongly induced by drought stress,.According to the metabolic pathway, drought stress induced PmNCED gene expression, and then PmNCED catalyzed ABA, further to resist drought. |
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