WHIRLY2 is a single‐stranded DNA binding protein associated with mitochondrial nucleoids. In the why 2‐1 mutant of Arabidopsis thaliana, a major proportion of leaf mitochondria has an aberrant structure characterized by disorganized nucleoids, reduced abundance of cristae, and a low matrix density despite the fact that the macroscopic phenotype during vegetative growth is not different from wild type. These features coincide with an impairment of the functionality and dynamics of mitochondria that have been characterized in detail in wild‐type and why 2‐1 mutant cell cultures. In contrast to the development of the vegetative parts, seed germination is compromised in the why 2‐1 mutant. In line with that, the expression level of why 2 in seeds of wild‐type plants is higher than that of why 3, whereas in adult plant no difference is found. Intriguingly, in early stages of shoots development of the why 2‐1 mutant, although not in seeds, the expression level of why 3 is enhanced. These results suggest that WHIRLY3 is a potential candidate to compensate for the lack of WHIRLY2 in the why 2‐1 mutant. Such compensation is possible only if the two proteins are localized in the same organelle. Indeed, in organello protein transport experiments using intact mitochondria and chloroplasts revealed that WHIRLY3 can be dually targeted into both, chloroplasts and mitochondria. Together, these data indicate that the alterations of mitochondria nucleoids are tightly linked to alterations of mitochondria morphology and functionality. This is even more evident in those phases of plant life when mitochondrial activity is particularly high, such as seed germination. Moreover, our results indicate that the differential expression of why 2 and why 3 predetermines the functional replacement of WHIRLY2 by WHIRLY3, which is restricted though to the vegetative parts of the plant.

中文翻译：

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WHIRLY2 在拟南芥线粒体形态、动力学和功能中发挥着关键作用。


WHIRLY2 是一种与线粒体核苷相关的单链 DNA 结合蛋白。在拟南芥的why 2-1突变体中，尽管营养生长期间的宏观表型与营养生长期间的宏观表型没有什么不同，但大部分叶线粒体具有异常结构，其特征是核仁紊乱、嵴丰度减少和基质密度低。野生型。这些特征与线粒体功能和动力学的损伤相一致，这些功能和动力学已在野生型和2-1突变细胞培养物中进行了详细表征。与营养部分的发育相反， why 2-1突变体的种子萌发受到损害。与此相符的是， why 2在野生型植物种子中的表达水平高于why 3的表达水平，而在成年植物中没有发现差异。有趣的是，在why 2-1突变体芽发育的早期阶段，尽管不是在种子中，但why 3的表达水平有所增强。这些结果表明 WHIRLY3 是弥补Why 2-1突变体中 WHIRLY2 缺失的潜在候选者。只有当两种蛋白质位于同一细胞器中时，这种补偿才有可能。事实上，在使用完整线粒体和叶绿体的细胞器蛋白质运输实验中表明，WHIRLY3 可以双重靶向叶绿体和线粒体。总之，这些数据表明线粒体核仁的改变与线粒体形态和功能的改变密切相关。这在植物生命中线粒体活性特别高的阶段（例如种子发芽）更加明显。 此外，我们的结果表明， why 2和why 3的差异表达预先决定了 WHIRLY3 对 WHIRLY2 的功能替代，但这仅限于植物的营养部分。