【作者】 张琳；

【导师】 夏继星；

【作者基本信息】 广西大学 ， 生物学， 2024， 硕士

【摘要】 凯氏带(Casparian strip,CS)是垂周细胞壁中的带状木质素结构,环绕邻近的内皮层细胞,密封维管植物的细胞外空间,是调节选择性营养吸收和离子稳态的重要屏障。水稻在内皮层和外皮层各有一个凯氏带。然而,水稻凯氏带形成的分子机制及其在调节选择性营养吸收中的作用机制并不清楚。在拟南芥中,转录因子At MYB36被报道是内皮层凯氏带形成的关键调控因子。水稻中有三个At MYB36的同源基因,分别是OsMYB36a、OsMYB36b和OsMYB36c。在本研究中,我们以OsMYB36a作为主要研究对象,通过对OsMYB36a的序列、表达模式、组织/细胞/亚细胞定位、下游基因的鉴定以及敲除突变体生理表型分析,揭示了OsMYB36a调控水稻根内皮层凯氏带形成的分子机制及其生理功能。主要研究结果如下:(1)OsMYB36a在水稻根部组织(尤其是距离根尖0-1 cm处)呈现高表达,且OsMYB36a几乎定位于水稻所有根细胞的细胞核;(2)OsMYB36a的敲除对水稻的株高、结实率、千粒重等农艺性状都有明显的抑制作用,木质素染色发现突变体中外皮层凯氏带的形成正常,但内皮层的凯氏带形成有缺陷;(3)OsMYB36a的敲除影响木质素和木栓质在内皮层的正确沉积,并破坏内皮层质外体屏障的完整性;(4)与野生型水稻相比,osmyb36a突变体表现出较高的Ca积累,而较低的K、Mg、Zn、Cu和Cd积累;外源的高浓度Ca处理进一步抑制了突变体的生长,同时在茎中积累了更多的Ca元素;(5)OsMYB36a在酵母中具有转录自激活能力,并且其激活结构域位于C末端;(6)转录组分析鉴定出1061个受OsMYB36a调控的下游基因,部分基因与凯氏带形成高度相关,OsMYB36a可直接激活OsCASP1和OsESB1基因启动子的转录活性。总之,我们的研究结果不仅表明OsMYB36a是水稻根内皮层凯氏带形成的关键调控基因,而且在一定程度上阐释了内皮层凯氏带在水稻根系选择性吸收Ca等矿物质元素中的作用机制。更多还原

【Abstract】 The Casparian strip(CS)is a belt-like lignin-based structure in the anticlinal cell wall encircling neighboring endodermal cells that seals the extracellular space in vascular plants.It is an important barrier regulating selective nutrient absorption and ion homeostasis.Rice roots have one CS in both the exodermis and endodermis,respectively.However,the molecular mechanism of CS formation in rice and its role in regulating selective nutrient uptake are poorly understood.In Arabidopsis,the transcription factor At MYB36 has been reported to be a key regulator in the formation of endodermal CS.There are three homologous genes of At MYB36 in rice,namely OsMYB36 a,OsMYB36 b,and OsMYB36 c.In this study,we mainly focused on OsMYB36 a.By analyzing its sequence,expression pattern,tissue/cell/subcellular localization,downstream genes,and physiological phenotype analysis of knockout mutants,we revealed the molecular mechanism and physiological function of OsMYB36 a in regulating the formation of endodermal CS in rice.The main findings are as follows:(1)OsMYB36 a is highly expressed in the root tissues,especially at0-1 cm from the root tip,and localized in the nucleus of most root cells in rice;(2)Knockout of OsMYB36 a has a significant inhibitory effect on agronomic traits such as plant height,seed setting rate,and the weight of a thousand seeds in rice.Lignin staining revealed that the formation of exodermal CS in the mutant is as normal as that in the wild type,but there were defects in endodermal CS;(3)Knockout of OsMYB36 a affects the correct deposition of lignin and suberin in endodermis,and disrupts the integrity of the extracellular barrier in endodermis;(4)Compared with wild-type rice,the osmyb36 a mutant showed higher Ca accumulation and lower K,Mg,Zn,Cu,and Cd accumulation.Exogenous high Ca treatment further inhibited the growth of mutants and accumulated more Ca in shoots;(5)OsMYB36 a has transcriptional activation in yeast,and its activation domain is located at the C-terminus;(6)Transcriptome analysis identified 1061 downstream genes regulated by OsMYB36 a,some of which are highly correlated with the CS formation.OsMYB36 a can directly activate the transcriptional activity of the promoters of OsCASP1 and OsESB1.In summary,our findings not only indicate that OsMYB36 a is a key regulatory gene for CS formation in endodermal CS,but also to some extent elucidate the role of CS in the selective absorption of mineral elements such as Ca by rice roots.更多还原