Boussardon Clément, Simon Matthieu, Carrie Chris, Fuszard Matthew, Meyer Etienne H, Budar Françoise, Keech Olivier
Department of Plant Physiology, UPSC, Umeå University, 90187 Umeå, Sweden.
Université Paris-Saclay, INRAE, AgroParisTech, Institut Jean-Pierre Bourgin (IJPB), 78000 Versailles, France.
Curr Biol. 2025 Feb 24;35(4):776-787.e5. doi: 10.1016/j.cub.2024.12.037. Epub 2025 Jan 28.
To propagate their genetic material, flowering plants rely on the production of large amounts of pollen grains that are capable of germinating on a compatible stigma. Pollen germination and pollen tube growth are thought to be extremely energy-demanding processes. This raises the question of whether mitochondria from pollen grains are specifically tuned to support this developmental process. To address this question, we isolated mitochondria from both mature pollen and floral buds using the isolation of mitochondria tagged in specific cell-type (IMTACT) strategy and examined their respective proteomes. Strikingly, mitochondria from mature pollen grains have lost many proteins required for genome maintenance, gene expression, and translation. Conversely, a significant accumulation of proteins associated with the tricarboxylic acid (TCA) cycle, the electron transport chain (ETC), and Ca homeostasis was observed. This supports the current model in which pollen requires large quantities of ATP for tube growth but also identifies an unexpected depletion of the gene expression machinery, aligned with the fact that the mitochondrial genome is actively degraded during pollen maturation. Altogether, our results uncover that mitochondria from mature pollen grains are strategically prepared for action by increasing their respiratory capacity and dismantling their gene expression machinery, which raises new questions about the assembly of respiratory complexes in pollen mitochondria, as they rely on the integration of proteins coded by the nuclear and mitochondrial genomes. In addition, the approach described here opens a new range of possibilities for studying mitochondria during pollen development and in pollen-specific mitochondrial events.
为了传播其遗传物质，开花植物依赖于产生大量能够在相容柱头上萌发的花粉粒。花粉萌发和花粉管生长被认为是极其耗能的过程。这就提出了一个问题，即花粉粒中的线粒体是否经过特殊调节以支持这一发育过程。为了解决这个问题，我们使用特定细胞类型标记线粒体分离（IMTACT）策略从成熟花粉和花芽中分离出线粒体，并检查它们各自的蛋白质组。令人惊讶的是，成熟花粉粒中的线粒体已经失去了许多基因组维护、基因表达和翻译所需的蛋白质。相反，观察到与三羧酸（TCA）循环、电子传递链（ETC）和钙稳态相关的蛋白质大量积累。这支持了当前的模型，即花粉管生长需要大量ATP，但也发现了基因表达机制的意外消耗，这与线粒体基因组在花粉成熟过程中被积极降解的事实一致。总之，我们的结果揭示，成熟花粉粒中的线粒体通过提高其呼吸能力和拆解其基因表达机制，为行动做好了战略准备，这就引发了关于花粉线粒体中呼吸复合体组装的新问题，因为它们依赖于核基因组和线粒体基因组编码的蛋白质的整合。此外，这里描述的方法为研究花粉发育过程中和花粉特异性线粒体事件中的线粒体开辟了一系列新的可能性。
