The Arabidopsis KINβγ Subunit of the SnRK1 Complex Regulates Pollen Hydration on the Stigma by Mediating the Level of Reactive Oxygen Species in Pollen.
The Arabidopsis KINβγ Subunit of the SnRK1 Complex Regulates Pollen Hydration on the Stigma by Mediating the Level of Reactive Oxygen Species in Pollen.
复制标题
SnRK1 复合物的拟南芥 KINβγ 亚基通过调节花粉中活性氧的水平来调节柱头上的花粉水合
DOI：
10.1371/journal.pgen.1006228
复制
发表时间：
2016-07
期刊：
影响因子：
4.5
通讯作者：
Zhang XS
中科院分区：
文献类型：
--
作者：
Gao XQ;Liu CZ;Li DD;Zhao TT;Li F;Jia XN;Zhao XY;Zhang XS
花粉与柱头的相互作用对花粉萌发至关重要。花粉萌发的过程包括花粉在柱头上的粘附、水合和萌发。然而，调节花粉-柱头相互作用的花粉内部信号转导机制却知之甚少。KINβγ是SNF 1相关蛋白激酶1复合物的一个植物特异性亚基，在植物发育调控中起重要作用。在这里，我们发现KINβγ在拟南芥花粉粒营养细胞中是一种细胞质和细胞核定位蛋白。拟南芥kinβγ突变体的花粉不能在柱头上萌发，但在离体条件下能正常萌发。进一步分析发现，kinβγ突变体花粉在柱头上的水合作用受到影响。然而，向柱头中加水促进了突变体花粉在体内的萌发，这表明突变体花粉的水合作用受损导致其萌发缺陷。在kinβγ突变体中，线粒体和过氧化物酶体的结构被破坏，数量明显减少。此外，我们发现kinβγ突变体表现出花粉中活性氧（ROS）水平降低。体外加入H2 O2部分补偿了突变花粉吸水性的降低，并且通过过表达拟南芥CATALASE 3降低花粉中的活性氧水平导致柱头上花粉的水合作用受到损害。这些结果表明，拟南芥KINβγ通过介导花粉中线粒体和过氧化物酶体的生物合成来调节ROS水平，这是授粉过程中花粉-柱头相互作用所必需的。花粉落在柱头上后，经过粘附和水合作用，萌发形成花粉管，这一过程中花粉与柱头的相互作用决定了花粉能否在柱头上萌发。近年来，人们从细胞和分子水平对自交不亲和系统中花粉与柱头之间的相互作用机制进行了广泛的研究。然而，很少有研究集中在自交亲和授粉过程中的花粉-柱头相互作用。拟南芥为研究自交亲和授粉过程中花粉与柱头的相互作用机制提供了一个良好的系统。KINβγ是SNF 1相关蛋白激酶1复合物的植物特异性亚基。在这项研究中，我们鉴定了一个拟南芥kinβγ突变体，该突变体的花粉在柱头表面萌发有缺陷，但在培养基上没有萌发，这是由于柱头上的花粉水合作用受损所致。进一步的分析表明，线粒体和过氧化物酶体的生物合成在该突变体中受损，从而降低了花粉中活性氧（ROS）的水平。应用H_2O_2可恢复花粉离体水化能力。这些结果表明，活性氧信号参与调控授粉过程中的花粉-柱头相互作用。本研究为进一步研究自交亲和植物花粉-柱头相互作用的机理提供了新的思路。
Pollen–stigma interactions are essential for pollen germination. The highly regulated process of pollen germination includes pollen adhesion, hydration, and germination on the stigma. However, the internal signaling of pollen that regulates pollen–stigma interactions is poorly understood. KINβγ is a plant-specific subunit of the SNF1-related protein kinase 1 complex which plays important roles in the regulation of plant development. Here, we showed that KINβγ was a cytoplasm- and nucleus-localized protein in the vegetative cells of pollen grains in Arabidopsis. The pollen of the Arabidopsis kinβγ mutant could not germinate on stigma, although it germinated normally in vitro. Further analysis revealed the hydration of kinβγ mutant pollen on the stigma was compromised. However, adding water to the stigma promoted the germination of the mutant pollen in vivo, suggesting that the compromised hydration of the mutant pollen led to its defective germination. In kinβγ mutant pollen, the structure of the mitochondria and peroxisomes was destroyed, and their numbers were significantly reduced compared with those in the wild type. Furthermore, we found that the kinβγ mutant exhibited reduced levels of reactive oxygen species (ROS) in pollen. The addition of H2O2 in vitro partially compensated for the reduced water absorption of the mutant pollen, and reducing ROS levels in pollen by overexpressing Arabidopsis CATALASE 3 resulted in compromised hydration of pollen on the stigma. These results indicate that Arabidopsis KINβγ is critical for the regulation of ROS levels by mediating the biogenesis of mitochondria and peroxisomes in pollen, which is required for pollen–stigma interactions during pollination. After landing on the stigma, pollen grains germinate and create pollen tubes following adhesion and hydration processes, during which pollen–stigma interactions determine whether the pollen grains can germinate on the stigma. In recent years, the interaction mechanisms between the pollen and stigma have been studied extensively at the cellular and molecular level in self-incompatibility systems. However, few studies have focused on pollen–stigma interactions during self-compatible pollination. Arabidopsis thaliana provides an excellent system to study the interaction mechanisms between the pollen and stigma during self-compatible pollination. KINβγ is a plant-specific subunit of the SNF1-related protein kinase 1 complex. In this study, we identified an Arabidopsis kinβγ mutant showing defective pollen germination on the surface of the stigma but not on the culture medium, which resulted from the compromised hydration of pollen on the stigma. Further analysis revealed that the biogenesis of mitochondria and peroxisomes was impaired in this mutant, which reduced the levels of reactive oxygen species (ROS) in pollen. Application of H2O2 recovered the capability of pollen to undergo hydration in vitro. These results suggest that ROS signaling is involved in the regulation of pollen–stigma interactions during pollination. This study provides new insights into the mechanism underlying pollen–stigma interactions in self-compatible plant species.