A Transcriptional Program for Arbuscule Degeneration during AM Symbiosis Is Regulated by MYB1
A Transcriptional Program for Arbuscule Degeneration during AM Symbiosis Is Regulated by MYB1
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DOI：
10.1016/j.cub.2017.03.003
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发表时间：
2017-04-24
期刊：
影响因子：
9.2
通讯作者：
Harrison, Maria J.
中科院分区：
文献类型：
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作者：
Floss, Daniela S.;Gomez, S. Karen;Harrison, Maria J.
在植物与丛枝菌根（AM）真菌形成内共生过程中，根皮层细胞被称为丛枝的分支菌丝定殖，其功能是与植物进行营养交换[1]。尽管它们具有积极的功能，但丛枝是短暂的结构，并且它们的发育之后是退化阶段，其中丛枝和周围的丛枝周膜和基质逐渐从根细胞中消失[2，3]。目前，根细胞在这一过程中的作用和潜在的调控机制尚不清楚。在这里，通过使用蒺藜苜蓿pt4突变体，其中丛枝过早退化[4]，我们鉴定了丛枝退化相关基因，其中38%预计编码分泌型水解酶，表明在丛枝和界面的分解中发挥作用。通过RNAi和插入突变体的分析，我们确定了一个共生特异性的MYB样转录因子（MYB 1），抑制丛枝变性mtpt 4。在myb1中，几个退化相关基因的表达减少。相反，在组成型过表达MYB1的根中，退化相关基因的表达增加，随后的共生发展受损。MYB1调节的基因表达通过DELLA蛋白增强，并且依赖于NSP1 [5]，而不是NSP2 [6]。此外，MYB 1与DELLA和NSP 1相互作用。我们的数据确定了一个转录程序的丛枝退化，并揭示其监管机构包括MYB1与两个转录调控因子，NSP1和DELLA，这两个功能在前面的阶段的共生。我们建议，转录因子的组合使用，使转录程序的顺序表达丛枝发育和退化。
During the endosymbiosis formed between plants and arbuscular mycorrhizal (AM) fungi, the root cortical cells are colonized by branched hyphae called arbuscules, which function in nutrient exchange with the plant [1]. Despite their positive function, arbuscules are ephemeral structures, and their development is followed by a degeneration phase, in which the arbuscule and surrounding periarbuscular membrane and matrix gradually disappear from the root cell [2, 3]. Currently, the root cell's role in this process and the underlying regulatory mechanisms are unknown. Here, by using a Medicago truncatula pt4 mutant in which arbuscules degenerate prematurely [4], we identified arbuscule degeneration-associated genes, of which 38% are predicted to encode secreted hydrolases, suggesting a role in disassembly of the arbuscule and interface. Through RNAiand analysis of an insertion mutant, we identified a symbiosis-specific MYB-like transcription factor (MYB1) that suppresses arbuscule degeneration in mtpt4. In myb1, expression of several degeneration-associated genes is reduced. Conversely, in roots constitutively overexpressing MYB1, expression of degeneration-associated genes is increased and subsequent development of symbiosis is impaired. MYB1-regulated gene expression is enhanced by DELLA proteins and is dependent on NSP1 [5], but not NSP2 [6]. Furthermore, MYB1 interacts with DELLA and NSP1. Our data identify a transcriptional program for arbuscule degeneration and reveal that its regulators include MYB1 in association with two transcriptional regulators, NSP1 and DELLA, both of which function in preceding phases of the symbiosis. We propose that the combinatorial use of transcription factors enables the sequential expression of transcriptional programs for arbuscule development and degeneration.