Ekawa Minako, Aoki Koh
Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-1 Gakuen-Cho, Naka-Ku, Sakai, Osaka 599-8531, Japan.
Plants (Basel). 2017 Dec 5;6(4):60. doi: 10.3390/plants6040060.
parasitizes a wide range of plants, including important crops, and causes serious damage to their production. develops a specialized intrusive organ called a haustorium that establishes connections to the host's xylem and phloem. In parallel with the development of xylem vessels, the differentiation of phloem-conducting cells has been demonstrated by the translocation of symplasmic tracers from the host to the parasite. However, it is unclear yet whether haustorial phloem-conducting cells are sieve elements. In this study, we identified phloem-conducting cells in haustoria by the host-to-parasite translocation of green fluorescent protein (GFP) from tomato sieve tubes. Haustorial GFP-conducting cells contained nuclei but not callose-rich sieve plates, indicating that phloem-conducting cells in haustoria differ from conventional sieve elements. To ascertain why the nuclei were not degenerated, expression of the homologs NAC-domain containing transcription factor (), NAC45/86-dependent exonuclease-domain protein 1 (), and was examined. However, these genes were more highly expressed in the haustorium than in tubercle protrusion, implying that nuclear degradation in haustoria may not be exclusively controlled by the /- regulatory pathway. Our results also suggest that the formation of plasmodesmata with large size exclusion limits is independent of nuclear degradation and callose deposition.
寄生于多种植物，包括重要农作物，并对其产量造成严重损害。它发育出一种名为吸器的特殊侵入器官，与宿主的木质部和韧皮部建立连接。与木质部导管的发育同时，通过共质体示踪剂从宿主向寄生物的转运，已证明了韧皮部传导细胞的分化。然而，吸器的韧皮部传导细胞是否为筛管分子尚不清楚。在本研究中，我们通过绿色荧光蛋白（GFP）从番茄筛管向寄生物的转运，鉴定了吸器中的韧皮部传导细胞。吸器中GFP传导细胞含有细胞核，但没有富含胼胝质的筛板，这表明吸器中的韧皮部传导细胞不同于传统的筛管分子。为了确定细胞核为何没有退化，我们检测了同源物含NAC结构域转录因子（）、NAC45/86依赖性核酸外切酶结构域蛋白1（）和的表达。然而，这些基因在吸器中的表达高于瘤状突起中的表达，这意味着吸器中细胞核的降解可能并非完全由/调控途径控制。我们的结果还表明，具有大尺寸排阻极限的胞间连丝的形成与细胞核降解和胼胝质沉积无关。
