摘要
[目的]研究玉蝉花(Iris ensata Thunb.)绿白嵌合叶片形成的机理,为植物花叶形成的生理机制研究提供理论参考.[方法]以花叶玉蝉花为供试材料,分别测定并比较了玉蝉花绿白部分叶绿素含量、叶片细胞和叶绿体结构、叶绿体合成前体物质以及叶绿素合成步骤关键酶的酶活性浓度,分析嵌合叶片绿白部分的差异.[结果]①花叶玉蝉花绿色部分和白色部分的叶绿素a、叶绿素b含量存在显著差异,均表现为绿色部分大于白色部分.②通过光学显微镜观察发现:白色组织的叶片细胞层间的叶绿体分布与数量与绿色组织存在显著的差异,明显低于绿色组织;且通过透射电镜观察发现:绿色组织叶绿体中类囊体膜结构较完整,拥有大量的淀粉颗粒和嗜锇颗粒,且拥有少量的液泡,而白色组织刚好相反.③叶绿体合成产物的相对含量表明:白色部分中的氨基乙酰丙酸(ALA)、胆色素原(PBG)、尿卟啉Ⅲ(Urogen Ⅲ)、粪卟啉Ⅲ(Coprogen Ⅲ)、原卟啉Ⅸ(Proto Ⅸ)、镁原卟啉Ⅸ(Mg-Proto Ⅸ)、原叶绿素酸酯(Pchlide)相较于绿色部分分别下降了34.31%、62.11%、36.28%、54.13%、65.49%、81.88%、91.61%.在CoprogenⅢ→ Proto Ⅸ→ Mg-Proto Ⅸ→ Pchlide合成步骤中,白色部分相较于绿色部分前体物质含量下降的比例依次升高.④通过花叶玉蝉花叶绿素合成前体物质含量的分析后,进一步测定Coprogen Ⅲ→ Proto Ⅸ合成步骤中原卟啉原Ⅸ酶活性浓度,发现白色部分相对于绿色部分酶活性浓度下降了90.44%.[结论]叶绿素的含量、发育和生物合成过程影响花叶玉蝉花绿白嵌合叶片的形成,并且在叶绿素的生物合成过程中,Coprogen Ⅲ→ Proto Ⅸ合成可能是其主要的受阻位点,导致叶绿素降低,玉蝉花出现花叶.
Abstract
[Objective]To study the formation mechanism of white-green mosaic leaves of Iris ensata'Variegata',and to provide theoretical reference for the physiological mechanism of mosaic leaf forma-tion.[Method]Using I.ensata as the experimental material,the chlorophyll content of the green and white parts of the I.ensata,leaf cell and chloroplast structure,precursor substances of chloroplast syn-thesis and enzyme activity concentrations related to the chlorophyll synthesis were measured and com-pared,and the difference between the green and white parts of the mosaic leaves was analyzed.[Result]① Significant differences in chlorophyll a and chlorophyll b levels were observed between the green and the white part of the I.ensata,with higher levels in the green part.② There were notable differences in the distribution and quantity of chloroplasts among the cell layers of white and green parts,with the for-mer exhibiting lower levels compared to the latter based on optical microscope observation.Transmission electron microscopy analysis revealed that chloroplasts in the green part exhibited a more intact thylakoid membrane structure,abundant starch granules and osmiophilic globules,and a small number of vacu-oles,in contrast to the white part which displayed the opposite characteristics.③ The analysis of chloro-plast synthesis products revealed a significant decrease in the relative contents of 5-Aminolevulinic acid(ALA),porphobilinogen(PBG),uroporphyrin III(Urogen III),coproporphyrin III(Coprogen III),pro-toporphyrin IX(Proto IX),magnesium protoporphyrin IX(Mg-Proto IX),and protochlorophyllide(Pch-lide)in the white part compared to the green part.Specifically,the white part exhibited reduction of 34.31%,62.11%,36.28%,54.13%,65.49%,81.88%and 91.61%in these respective compounds.In the synthesis steps of Coprogen III→ Proto IX→ Mg-Proto IX→ Pchlide,there was a successive in-crease in the proportion of precursor substance content decreasing in the white part compared to the green part.④ After analyzing the content of the precursor substances for chlorophyll synthesis,the activity con-centration of the protoporphyrinogen IX enzyme in the Coprogen III→ Proto IX synthesis step was further determined,and it was found that the activity concentration in the white part decreased by 90.44%in comparison to the green part.[Conclusion]The formation of white-green mosaic leaves of I.ensata is in-fluenced by chlorophyll content,development and biosynthesis processes.It is hypothesized that the ma-jor blocked site during chlorophyll biosynthesis in this species is the conversion of Coprogen III→ Proto IX,leading to decreased chlorophyll levels and the appearance of variegated leaves of I.ensata.
基金项目
四川省科技厅自然科学基金(2022NSFSC1049)
国家自然科学基金(22206140)
NETL
NSTL
万方数据