Tapetosomes in Brassica tapetum accumulate endoplasmic reticulum-derived flavonoids and alkanes for delivery to the pollen surface
Tapetosomes in Brassica tapetum accumulate endoplasmic reticulum-derived flavonoids and alkanes for delivery to the pollen surface
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DOI：
10.1105/tpc.106.049049
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发表时间：
2007-02-01
期刊：
影响因子：
11.6
通讯作者：
Huang, Anthony H. C.
中科院分区：
文献类型：
--
作者：
Hsieh, Kai;Huang, Anthony H. C.
绒毡体是菊科植物花粉成熟活跃期绒毡层细胞中丰富的细胞器。它们具有内质网（ER）衍生的囊泡和油质蛋白包被的脂滴，但它们的总体组成和功能尚未确定。油菜花药原位定位分析显示，黄酮类化合物只存在于绒毡层细胞中，首先在内质网沿着与黄酮-39-羟化酶，然后在内质网衍生的绒毡体。黄色素在细胞质、弹性体、液泡和细胞核中均不存在。发育中花药的亚细胞分级定位于绒毡层体中的类黄酮和烷烃。亚绒毡体分馏本地化类黄酮在ER衍生的囊泡，和烷烃和油质蛋白的脂滴。绒毡层细胞死亡后，黄酮类化合物，烷烃和油质蛋白位于成熟花粉。在拟南芥突变体TT 12和TT 19缺乏类黄酮转运蛋白，类黄酮存在于细胞质中的量减少，但不存在于绒毡体，随后位于成熟的花粉。tt 4、tt 12和tt 19花粉比野生型花粉更易受UV-B辐射影响而萌发。因此，绒毡层体积累ER衍生的类黄酮、烷烃和油质蛋白，以便在细胞死亡时排放到花粉表面。这种绒毡层起源的花粉衣保护单倍型花粉免受紫外线伤害和水分损失，并有助于水分吸收。
Tapetosomes are abundant organelles in tapetum cells during the active stage of pollen maturation in Brassicaceae species. They possess endoplasmic reticulum (ER)-derived vesicles and oleosin- coated lipid droplets, but their overall composition and function have not been established. In situ localization analyses of developing Brassica napus anthers revealed flavonoids present exclusively in tapetum cells, first in an ER network along with flavonoid-39-hydroxylase and then in ER-derived tapetosomes. Flavonoids were absent in the cytosol, elaioplasts, vacuoles, and nuclei. Subcellular fractionation of developing anthers localized both flavonoids and alkanes in tapetosomes. Subtapetosome fractionation localized flavonoids in ERderived vesicles, and alkanes and oleosins in lipid droplets. After tapetum cell death, flavonoids, alkanes, and oleosins were located on mature pollen. In the Arabidopsis thaliana mutants tt12 and tt19 devoid of a flavonoid transporter, flavonoids were present in the cytosol in reduced amounts but absent in tapetosomes and were subsequently located on mature pollen. tt4, tt12, and tt19 pollen was more susceptible than wild-type pollen to UV-B irradiation on subsequent germination. Thus, tapetosomes accumulate ER-derived flavonoids, alkanes, and oleosins for discharge to the pollen surface upon cell death. This tapetosome-originated pollen coat protects the haploidic pollen from UV light damage and water loss and aids water uptake.