BcMF9 是一个新型的多聚半乳糖醛酸酶基因，它对于芸薹属内、外壁层的形成都是必需的。
BcMF9, a novel polygalacturonase gene, is required for both Brassica campestris intine and exine formation.
机构信息
Laboratory of Cell & Molecular Biology, Institute of Vegetable Science, Zhejiang University, Hangzhou 310029, China.
出版信息
Ann Bot. 2009 Dec;104(7):1339-51. doi: 10.1093/aob/mcp244. Epub 2009 Oct 8.
BACKGROUND AND AIMS
The polygalacturonase (PG) gene family has been found to be enriched in pollen of several species; however, little is currently known about the function of the PG gene in pollen development. To investigate the exact role that the PG gene has played in pollen development and about this family in general, one putative PG gene, Brassica campestris Male Fertility 9 (BcMF9), was isolated from Chinese cabbage (Brassica campestris ssp. chinensis, syn. B. rapa ssp. chinensis) and characterized.
METHODS
RT-PCR, northern blotting and in situ hybridization were used to analyse the expression pattern of BcMF9, and antisense RNA technology was applied to study the function of this gene.
KEY RESULTS
BcMF9 is expressed in particular in the tapetum and microspore during the late stages of pollen development. Antisense RNA transgenic plants that displayed decreased expression of BcMF9 showed pollen morphological defects that resulted in reduced pollen germination efficiency. Transmission electron microscopy revealed that the homogeneous pectic exintine layer of pollen facing the exterior was over-developed and predominantly occupied the intine, reversing the normal proportional distribution of the internal endintine layer and the external exintine in transgenic pollen. Inhibition of BcMF9 also resulted in break-up of the previously formed tectum and baculae from the beginning of the binucleate stage, as a result of premature degradation of tapetum.
CONCLUSIONS
Several lines of evidence, including patterns of BcMF9 expression and phenotypic defects, suggest a sporophytic role in exine patterning, and a gametophytic mode of action of BcMF9 in intine formation. BcMF9 might act as a co-ordinator in the late stages of tapetum degeneration, and subsequently in the regulation of wall material secretion and, in turn, exine formation. BcMF9 might also play a role in intine formation, possibly via regulation of the dynamic metabolism of pectin.
背景和目的
已发现多聚半乳糖醛酸酶（PG）基因家族在几个物种的花粉中富集；然而，目前对于 PG 基因在花粉发育中的功能知之甚少。为了研究 PG 基因在花粉发育中的确切作用以及该基因家族的一般功能，从白菜（芸薹 Brassica campestris ssp. chinensis，同芸薹 Brassica rapa ssp. chinensis）中分离出一个假定的 PG 基因，甘蓝雄性不育 9 号基因（BcMF9），并对其进行了特征分析。
方法
采用 RT-PCR、 northern 印迹和原位杂交分析 BcMF9 的表达模式，并应用反义 RNA 技术研究该基因的功能。
主要结果
BcMF9 在花粉发育后期的绒毡层和小孢子中特异性表达。显示 BcMF9 表达降低的反义 RNA 转基因植物表现出花粉形态缺陷，导致花粉萌发效率降低。透射电子显微镜显示，花粉面对外部的同质果胶外壁层过度发育，主要占据内壁，使正常的内、外壁层的比例分布在转基因花粉中发生逆转。BcMF9 的抑制也导致从双核期开始，先前形成的纹饰和小刺从绒毡层开始解体，这是由于绒毡层过早降解的结果。
结论
包括 BcMF9 表达模式和表型缺陷在内的几条证据表明，BcMF9 在花粉外壁模式形成中具有孢子体作用，在花粉内壁形成中具有配子体作用。BcMF9 可能作为绒毡层退化晚期的协调因子，随后调节细胞壁物质的分泌，并继而影响外壁的形成。BcMF9 可能也参与了内壁的形成，可能是通过调节果胶的动态代谢。
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