Muellender Maximilian M, Savenkov Eugene I, Reichelt Michael, Varrelmann Mark, Liebe Sebastian
Institute of Sugar Beet Research, Department of Phytopathology, Göttingen, Germany.
Department of Plant Biology, Uppsala BioCenter SLU, Swedish University of Agricultural Sciences, Linnean Center for Plant Biology, Uppsala, Sweden.
Front Microbiol. 2022 Jan 24;12:809690. doi: 10.3389/fmicb.2021.809690. eCollection 2021.
Rhizomania caused by Beet necrotic yellow vein virus (BNYVV) is characterized by excessive lateral root (LR) formation. Auxin-mediated degradation of Aux/IAA transcriptional repressors stimulates gene regulatory networks leading to LR organogenesis and involves several Aux/IAA proteins acting at distinctive stages of LR development. Previously, we showed that BNYVV p25 virulence factor interacts with BvIAA28, a transcriptional repressor acting at early stages of LR initiation. The evidence suggested that p25 inhibits BvIAA28 nuclear localization, thus, de-repressing transcriptional network leading to LR initiation. However, it was not clear whether p25 interacts with other Aux/IAA proteins. Here, by adopting bioinformatics, and protein interaction approaches we show that p25 interacts also with BvIAA2 and BvIAA6. Moreover, we confirmed that the BNYVV infection is, indeed, accompanied by an elevated auxin level in the infected LRs. Nevertheless, expression levels of BvIAA2 and BvIAA6 remained unchanged upon BNYVV infection. Mutational analysis indicated that interaction of p25 with either BvIAA2 or BvIAA6 requires full-length proteins as even single amino acid residue substitutions abolished the interactions. Compared to p25-BvIAA28 interaction that leads to redistribution of BvIAA28 into cytoplasm, both BvIAA2 and BvIAA6 remained confined into the nucleus regardless of the presence of p25 suggesting their stabilization though p25 interaction. Overexpression of p25-interacting partners (BvIAA2, BvIAA6 and BvIAA28) in induced an auxin-insensitive phenotype characterized by plant dwarfism and dramatically reduced LR development. Thus, our work reveals a distinct class of transcriptional repressors targeted by p25.
由甜菜坏死黄脉病毒（BNYVV）引起的根肿病的特征是侧根（LR）过度形成。生长素介导的Aux/IAA转录抑制因子的降解刺激了导致LR器官发生的基因调控网络，并且涉及几种在LR发育的不同阶段起作用的Aux/IAA蛋白。此前，我们发现BNYVV p25毒力因子与BvIAA28相互作用，BvIAA28是一种在LR起始早期起作用的转录抑制因子。证据表明，p25抑制BvIAA28的核定位，从而解除对导致LR起始的转录网络的抑制。然而，尚不清楚p25是否与其他Aux/IAA蛋白相互作用。在这里，通过采用生物信息学和蛋白质相互作用方法，我们表明p25也与BvIAA2和BvIAA6相互作用。此外，我们证实BNYVV感染确实伴随着受感染LR中生长素水平的升高。然而，BNYVV感染后BvIAA2和BvIAA6的表达水平保持不变。突变分析表明，p25与BvIAA2或BvIAA6的相互作用需要全长蛋白，因为即使单个氨基酸残基的替换也会消除这种相互作用。与导致BvIAA28重新分布到细胞质中的p25-BvIAA28相互作用相比，无论p25是否存在，BvIAA2和BvIAA6都保留在细胞核中，这表明它们通过与p25相互作用而得到稳定。在 中过表达与p25相互作用的伙伴（BvIAA2、BvIAA6和BvIAA28）会诱导一种生长素不敏感表型，其特征是植株矮小且LR发育显著减少。因此，我们的工作揭示了一类由p25靶向的独特转录抑制因子。
