Apple S-RNase triggers inhibition of tRNA aminoacylation by interacting with a soluble inorganic pyrophosphatase in growing self-pollen tubes invitro
Apple S-RNase triggers inhibition of tRNA aminoacylation by interacting with a soluble inorganic pyrophosphatase in growing self-pollen tubes invitro
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苹果 S-RNase 通过与体外生长的自体花粉管中的可溶性无机焦磷酸酶相互作用，触发 tRNA 氨酰化的抑制
DOI：
10.1111/nph.15028
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发表时间：
2018-04-01
期刊：
影响因子：
9.4
通讯作者：
Li, Tianzhong
中科院分区：
文献类型：
--
作者：
Li, Wei;Meng, Dong;Li, Tianzhong
苹果表现出基于S-RNase的自交不亲和性（SI），其中S-RNase在拒绝自交花粉中起核心作用。有人提出，茄科植物SI中花粉生长停滞是S-RNase降解花粉rRNA的结果；然而，玫瑰科的潜在机制尚不清楚。本文以S-2-RNase为诱饵，筛选了苹果花粉cDNA文库，并鉴定了与s - rnase物理相互作用的苹果可溶性无机焦磷酸酶（MdPPa）。自s - rnase处理后，苹果花粉管的生长受到明显抑制，内源可溶性焦磷酸酶活性降低，无机焦磷酸盐（PPi）水平升高。此外，S-RNase被发现与MdPPa的两个可变区域结合，导致其活性的非竞争性抑制。沉默MdPPa表达导致花粉管生长减少。有趣的是，在自s - rnase处理或mdppa沉默的花粉管中，tRNA氨基酰化被抑制，导致未带电tRNA的积累。此外，我们提供的证据表明，tRNA氨基酰化的这种干扰是独立于RNase活性。我们提出了一种不同于RNA降解的替代机制来解释S-RNase苹果SI过程的细胞毒性。
Apple exhibits S-RNase-based self-incompatibility (SI), in which S-RNase plays a central role in rejecting self-pollen. It has been proposed that the arrest of pollen growth in SI of Solanaceae plants is a consequence of the degradation of pollen rRNA by S-RNase; however, the underlying mechanism in Rosaceae is still unclear. Here, we used S-2-RNase as a bait to screen an apple pollen cDNA library and characterized an apple soluble inorganic pyrophosphatase (MdPPa) that physically interacted with S-RNases. When treated with self S-RNases, apple pollen tubes showed a marked growth inhibition, as well as a decrease in endogenous soluble pyrophosphatase activity and elevated levels of inorganic pyrophosphate (PPi). In addition, S-RNase was found to bind to two variable regions of MdPPa, resulting in a noncompetitive inhibition of its activity. Silencing of MdPPa expression led to a reduction in pollen tube growth. Interestingly, tRNA aminoacylation was inhibited in self S-RNase-treated or MdPPa-silenced pollen tubes, resulting in the accumulation of uncharged tRNA. Furthermore, we provide evidence showing that this disturbance of tRNA aminoacylation is independent of RNase activity. We propose an alternative mechanism differing from RNA degradation to explain the cytotoxicity of the S-RNase apple SI process.