Anhui Province Key Laboratory of Horticultural Crop Quality Biology, College of Horticulture, Anhui Agricultural University, 130 West Changjiang Road, Hefei City 230036, Anhui Province, People's Republic of China.
State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, 130 West Changjiang Road, Hefei City 230036, Anhui Province, People's Republic of China.
J Exp Bot. 2024 May 20;75(10):3054-3069. doi: 10.1093/jxb/erae042.
Phytoplasmas manipulate host plant development to benefit insect vector colonization and their own invasion. However, the virulence factors and mechanisms underlying small-leaf formation caused by jujube witches' broom (JWB) phytoplasmas remain largely unknown. Here, effectors SJP1 and SJP2 from JWB phytoplasmas were identified to induce small-leaf formation in jujube (Ziziphus jujuba). In vivo interaction and expression assays showed that SJP1 and SJP2 interacted with and stabilized the transcription factor ZjTCP2. Overexpression of SJP1 and SJP2 in jujube induced ZjTCP2 accumulation. In addition, the abundance of miRNA319f_1 was significantly reduced in leaves of SJP1 and SJP2 transgenic jujube plants and showed the opposite pattern to the expression of its target, ZjTCP2, which was consistent with the pattern in diseased leaves. Overexpression of ZjTCP2 in Arabidopsis promoted ectopic leaves arising from the adaxial side of cotyledons and reduced leaf size. Constitutive expression of the miRNA319f_1 precursor in the 35S::ZjTCP2 background reduced the abundance of ZjTCP2 mRNA and reversed the cotyledon and leaf defects in Arabidopsis. Therefore, these observations suggest that effectors SJP1 and SJP2 induced small-leaf formation, at least partly, by interacting with and activating ZjTCP2 expression both at the transcriptional and the protein level, providing new insights into small-leaf formation caused by phytoplasmas in woody plants.
植原体操纵寄主植物的发育，有利于昆虫载体的定殖和自身的入侵。然而，导致枣树扫帚病（JWB）植原体形成小叶片的毒力因子和机制在很大程度上仍不清楚。在这里，鉴定出 JWB 植原体的效应子 SJP1 和 SJP2 可诱导枣（Ziziphus jujuba）形成小叶片。体内相互作用和表达分析表明，SJP1 和 SJP2 与转录因子 ZjTCP2 相互作用并稳定其表达。SJP1 和 SJP2 在枣中的过表达诱导 ZjTCP2 积累。此外，miRNA319f_1 在 SJP1 和 SJP2 转基因枣树叶片中的丰度显著降低，其表达模式与靶基因 ZjTCP2 的表达模式相反，与病叶的表达模式一致。ZjTCP2 在拟南芥中的过表达促进了子叶腹侧的异位叶片的产生，并减小了叶片的大小。35S::ZjTCP2 背景下 miRNA319f_1 前体的组成型表达降低了 ZjTCP2 mRNA 的丰度，并逆转了拟南芥中子叶和叶片的缺陷。因此，这些观察结果表明，效应子 SJP1 和 SJP2 通过与 ZjTCP2 相互作用并在转录和蛋白水平上激活其表达，至少部分诱导小叶片的形成，为木质植物中植原体引起的小叶片形成提供了新的见解。
