Kasaras Alexis, Melzer Michael, Kunze Reinhard
Dahlem Centre of Plant Sciences (DCPS), Freie Universität Berlin, Institut für Biologie - Angewandte Genetik, Berlin, Germany.
BMC Plant Biol. 2012 Apr 24;12:54. doi: 10.1186/1471-2229-12-54.
Arabidopsis DMP1 was discovered in a genome-wide screen for senescence-associated membrane proteins. DMP1 is a member of a novel plant-specific membrane protein family of unknown function. In rosette leaves DMP1 expression increases from very low background level several 100fold during senescence progression.
Expression of AtDMP1 fused to eGFP in Nicotiana benthamiana triggers a complex process of succeeding membrane remodeling events affecting the structure of the endoplasmic reticulum (ER) and the vacuole. Induction of spherical structures ("bulbs"), changes in the architecture of the ER from tubular to cisternal elements, expansion of smooth ER, formation of crystalloid ER, and emergence of vacuolar membrane sheets and foamy membrane structures inside the vacuole are proceeding in this order. In some cells it can be observed that the process culminates in cell death after breakdown of the entire ER network and the vacuole. The integrity of the plasma membrane, nucleus and Golgi vesicles are retained until this stage. In Arabidopsis thaliana plants expressing AtDMP1-eGFP by the 35S promoter massive ER and vacuole vesiculation is observed during the latest steps of leaf senescence, whereas earlier in development ER and vacuole morphology are not perturbed. Expression by the native DMP1 promoter visualizes formation of aggregates termed "boluses" in the ER membranes and vesiculation of the entire ER network, which precedes disintegration of the central vacuole during the latest stage of senescence in siliques, rosette and cauline leaves and in darkened rosette leaves. In roots tips, DMP1 is strongly expressed in the cortex undergoing vacuole biogenesis.
Our data suggest that DMP1 is directly or indirectly involved in membrane fission during breakdown of the ER and the tonoplast during leaf senescence and in membrane fusion during vacuole biogenesis in roots. We propose that these properties of DMP1, exacerbated by transient overexpression, may cause or contribute to the dramatic membrane remodeling events which lead to cell death in infiltrated tobacco leaves.
拟南芥DMP1是在全基因组衰老相关膜蛋白筛选中发现的。DMP1是一个功能未知的新型植物特异性膜蛋白家族的成员。在莲座叶中，DMP1的表达在衰老过程中从极低的背景水平增加数百倍。
在本氏烟草中表达与eGFP融合的AtDMP1会引发一系列复杂的膜重塑事件，影响内质网（ER）和液泡的结构。球形结构（“球茎”）的诱导、ER结构从管状元件向扁平囊状元件的变化、光滑ER的扩张、晶体状ER的形成以及液泡内液泡膜片层和泡沫状膜结构的出现按此顺序进行。在一些细胞中可以观察到，该过程在整个ER网络和液泡解体后以细胞死亡告终。直到这个阶段，质膜、细胞核和高尔基体囊泡的完整性得以保留。在通过35S启动子表达AtDMP1-eGFP的拟南芥植物中，在叶片衰老的最后阶段观察到大量的ER和液泡囊泡化，而在发育早期ER和液泡形态未受干扰。通过天然DMP1启动子表达可观察到ER膜中称为“团块”的聚集体的形成以及整个ER网络的囊泡化，这在角果、莲座叶和茎生叶以及黑暗处理的莲座叶衰老的最后阶段中央液泡解体之前发生。在根尖中，DMP1在经历液泡生物发生的皮层中强烈表达。
我们的数据表明，DMP1在叶片衰老过程中内质网和液泡膜破裂期间直接或间接参与膜裂变，在根中液泡生物发生期间参与膜融合。我们提出，DMP1的这些特性因瞬时过表达而加剧，可能导致或促成导致浸润烟草叶片细胞死亡的剧烈膜重塑事件。
