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谷子是中国北方重要杂粮作物,米色是评价谷子品质的重要指标,目前关于谷子米色的形成机制仍不明确。本研究选用米色分别为深黄、浅黄、白色和绿色的谷子品种各2个,对这8个谷子品种进行了总类胡萝卜素含量、β-胡萝卜素含量与米色差异间关系的分析,以及分子水平4个β-胡萝卜素代谢相关基因在籽粒不同灌浆阶段的表达模式分析,结果表明:CCI指数作为米色测定的综合指标,可对不同品种米色差异进行鉴定,且分别与总类胡萝卜素、β-胡萝卜素含量呈显著与极显著正相关。通过对8个品种SiLCYB基因组DNA克隆发现,只有深黄品种JG21中出现序列变异,有两个SNP位点,且第二处单核苷酸变异使相应氨基酸由谷氨酰胺变为精氨酸。SiLCYB表达不具有组织特异性,在叶中表达最高,茎中最低。通过对籽粒不同灌浆阶段β-胡萝卜素合成基因SiLCYB与另外3个β-胡萝卜素代谢相关基因(SiLCYBLCYE,SiHYD,SiCCD1)的表达分析发现:SiLCYB在大多数品种中表达基本恒定,且与β-胡萝卜素积累没有表现出显著相关性;而SiLCYE在不同品种中普遍呈现出与SiLCYB同增同减的表达模式,但表达水平低于SiLCYB;同时发现2个降解相关基因(SiHYD,SiCCD1)的表达与β-胡萝卜素积累在灌浆特定阶段表现出了显著或极显著负相关。因此,推测SiLCYB与降解基因SiHYD和SiCCD1共同作用,通过影响β-胡萝卜素和总类胡萝卜素在籽粒中的积累,进而影响米色的形成。
Millet is an important cereal crop in northern China. Beige is an important index for evaluating the quality of millet. At present, the formation mechanism of millet millet is still not clear. In this study, two dark-yellow, light-yellow, white and green millet varieties were selected, and the total carotenoid content and the relationship between β-carotene content and beige color were analyzed. The results showed that the CCI index could be used as a comprehensive index to determine the beige color, and the beige color differences of different varieties could be identified. The CCI index was correlated with the total carotenoid, β - carotene content was significantly and extremely significant positive correlation. By cloning the genomic DNA of 8 varieties of SiLCYB, we found that there were two SNP sites in the deep-yellow variety JG21, and the second single nucleotide mutation changed the corresponding amino acid from glutamine to arginine. SiLCYB expression was not tissue specific, highest expression in the leaves, the lowest stem. The expression analysis of SiLCYB and three other genes related to β-carotene metabolism (SiLCYBLCYE, SiHYD, SiCCD1) at different grain filling stages showed that SiLCYB was almost constant in most varieties, There was no significant correlation between carotenoid accumulation and expression of SiLCYB in SiLCYB cells. However, expression of SiLCYB protein was lower than that of SiLCYB protein in all the samples, and expression of two genes related to degradation (SiHYD, SiCCD1) And β-carotene accumulation in the grouting at a particular stage showed a significant or very significant negative correlation. Therefore, it is speculated that SiLCYB and degradation genes SiHYD and SiCCD1 together affect the formation of beige by affecting the accumulation of β-carotene and total carotenoids in the grain.