Ubiquitination of S4-RNase by S-LOCUS F-BOX LIKE2 Contributes to Self-Compatibility of Sweet Cherry 'Lapins'
Ubiquitination of S4-RNase by S-LOCUS F-BOX LIKE2 Contributes to Self-Compatibility of Sweet Cherry 'Lapins'
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DOI：
10.1104/pp.20.01171
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发表时间：
2020-12-01
期刊：
影响因子：
7.4
通讯作者：
Li, Wei
中科院分区：
文献类型：
--
作者：
Li, Yang;Duan, Xuwei;Li, Wei
F-box蛋白有助于甜樱桃'Lapins'的自交亲和性。最近的研究表明，甜樱桃（Prunus avium）S-4 '花粉中花粉S功能的丧失与S单倍型特异性F-box 4（SFB 4）基因的突变有关。然而，这种突变如何导致自交不亲和性尚不清楚。在这里，我们研究了这一机制，通过分析几个自交亲和甜樱桃品种。我们确定S4 '花粉（携带SFB 4'基因的花粉）中突变的SFB 4（SFB 4 '）比野生型SFB 4短约6 kD，这是由于四个核苷酸缺失引起的过早终止。SFB 4 ′不与S-RNase相互作用。然而，S4 '花粉中的一种蛋白质泛素化S-RNase，导致其通过26 S蛋白酶体途径降解，表明S4 '花粉中除SFB 4外的其他因子参与S-RNase的识别和降解。为了鉴定这些因子，我们使用S-4-RNase作为诱饵筛选S4 '花粉蛋白。我们的筛选鉴定了由S-4-SLFL 2编码的蛋白质，S-4-SLFL 2是与S-位点紧密连锁的低多态性基因。进一步的研究表明，SLFL 2泛素化S-RNase，导致其降解。亚细胞定位分析表明，SFB 4主要定位于花粉管顶端，而SLFL 2则不定位。当野生型花粉管中S-4-SLFL 2的表达被反义寡核苷酸抑制时，花粉仍然具有泛素化S-RNase的能力;然而，这种泛素标记的S-RNase不通过26 S蛋白酶体途径降解，表明SFB 4不参与S-RNase的降解。当SFB 4丧失功能时，S-4-SLFL 2可能介导S-RNase的泛素化和降解，这与S4 '花粉的自交亲和性一致。
An F-box protein contributes to the self-compatibility of sweet cherry 'Lapins'. Recent studies have shown that loss of pollen-S function in S-4 ' pollen from sweet cherry (Prunus avium) is associated with a mutation in an S haplotype-specific F-box4 (SFB4) gene. However, how this mutation leads to self-compatibility is unclear. Here, we examined this mechanism by analyzing several self-compatible sweet cherry varieties. We determined that mutated SFB4 (SFB4') in S4 ' pollen (pollen harboring the SFB4' gene) is approximately 6 kD shorter than wild-type SFB4 due to a premature termination caused by a four-nucleotide deletion. SFB4 ' did not interact with S-RNase. However, a protein in S4 ' pollen ubiquitinated S-RNase, resulting in its degradation via the 26S proteasome pathway, indicating that factors in S4 ' pollen other than SFB4 participate in S-RNase recognition and degradation. To identify these factors, we used S-4-RNase as a bait to screen S4 ' pollen proteins. Our screen identified the protein encoded by S-4-SLFL2, a low-polymorphic gene that is closely linked to the S-locus. Further investigations indicate that SLFL2 ubiquitinates S-RNase, leading to its degradation. Subcellular localization analysis showed that SFB4 is primarily localized to the pollen tube tip, whereas SLFL2 is not. When S-4-SLFL2 expression was suppressed by antisense oligonucleotide treatment in wild-type pollen tubes, pollen still had the capacity to ubiquitinate S-RNase; however, this ubiquitin-labeled S-RNase was not degraded via the 26S proteasome pathway, suggesting that SFB4 does not participate in the degradation of S-RNase. When SFB4 loses its function, S-4-SLFL2 might mediate the ubiquitination and degradation of S-RNase, which is consistent with the self-compatibility of S4 ' pollen.