SMALL AUXIN UP RNA62/75 Are Required for the Translation of Transcripts Essential for Pollen Tube Growth
SMALL AUXIN UP RNA62/75 Are Required for the Translation of Transcripts Essential for Pollen Tube Growth
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DOI：
10.1104/pp.18.00257
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发表时间：
2018-10-01
期刊：
影响因子：
7.4
通讯作者：
Jauh, Guang-Yuh
中科院分区：
文献类型：
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作者：
He, Siou-Luan;Hsieh, Hsu-Liang;Jauh, Guang-Yuh
成功的花粉管伸长对双受精至关重要，但花粉管基因的生物学功能和这一关键过程背后的调控机制在很大程度上尚不清楚。先前的一项转译基因组学研究揭示了两个拟南芥SAUR(小生长素上调RNA)基因，SAUR62和SAUR75，它们的表达受授粉上调。在这里，我们发现SAUR62和SAUR75主要定位于花粉管核。纯合的saur62(saur62/-)、saur75(saur75/-)和SAUR62/75RNA干扰(RNAi)基因敲除系的角果有许多败育的种子。这些品系具有正常的花粉活力，但在体内外花粉管生长存在缺陷，并具有分枝表型。转基因SAUR62/75-GFP花的免疫沉淀表明核糖体蛋白RPL12家族成员是潜在的相互作用伙伴，酵母双杂交和双分子荧光互补分析进一步证实了它们之间的个体相互作用。多聚体图谱显示，在纯合的SAUR62、SAUR75、核糖体大亚基12c和SAUR62/75RNAi花中，80S核糖体丰度降低，这表明SAUR62/75在核糖体组装中发挥作用。为了阐明它们在翻译中的作用，我们用等压标记对RNAi和野生型花的总蛋白进行了相对和绝对定量分析，发现参与花粉管壁生物发生的因子和F-肌动蛋白动态的表达显著减少，这是管伸长弹性特性的关键。事实上，RNAi花粉管显示了脱酯和酯化果胶以及F-肌动蛋白组织的错误定位。因此，SAUR62/75及其RPL12在核糖体60S前亚基组装中的生物学作用对于有效地延长花粉管和随后的受精至关重要。
Successful pollen tube elongation is critical for double fertilization, but the biological functions of pollen tube genes and the regulatory machinery underlying this crucial process are largely unknown. A previous translatomic study revealed two Arabidopsis (Arabidopsis thaliana) SAUR (SMALL AUXIN UP RNA) genes, SAUR62 and SAUR75, whose expression is up-regulated by pollination. Here, we found that both SAUR62 and SAUR75 localized mainly to pollen tube nuclei. The siliques of homozygous saur62 (saur62/-), saur75 (saur75/-), and the SAUR62/75 RNA interference (RNAi) knockdown line had many aborted seeds. These lines had normal pollen viability but defective in vitro and in vivo pollen tube growth, with branching phenotypes. Immunoprecipitation with transgenic SAUR62/75-GFP flowers revealed ribosomal protein RPL12 family members as potential interacting partners, and their individual interactions were confirmed further by yeast two-hybrid and bimolecular fluorescence complementation assays. Polysome profiling showed reduced 80S ribosome abundance in homozygous saur62, saur75, ribosomal large subunit12c, and SAUR62/75 RNAi flowers, suggesting that SAUR62/75 play roles in ribosome assembly. To clarify their roles in translation, we analyzed total proteins from RNAi versus wild-type flowers by isobaric tags for relative and absolute quantitation, revealing significantly reduced expression of factors participating in pollen tube wall biogenesis and F-actin dynamics, which are critical for the elastic properties of tube elongation. Indeed, RNAi pollen tubes showed mislocalization of deesterified and esterified pectins and F-actin organization. Thus, the biological roles of SAUR62/75 and their RPL12 partners are critical in ribosomal pre-60S subunit assembly for efficient pollen tube elongation and subsequent fertilization.