Krone Raissa, Gerlich Silke, Mertens Mette, Koprivova Anna, Westhoff Philipp, Kopriva Stanislav
Institute for Plant Sciences, Cluster of Excellence on Plant Sciences (CEPLAS), University of Cologne, Zülpicher Str. 47b, Cologne 50674, Germany.
Plant Metabolism and Metabolomics Facility, Cluster of Excellence on Plant Sciences (CEPLAS), Heinrich Heine University, Düsseldorf 40225, Germany.
Plant Physiol. 2025 Aug 4;198(4). doi: 10.1093/plphys/kiaf327.
C4 photosynthesis concentrates CO2 around Rubisco, thereby decreasing photorespiration and leading to greater productivity. C4 photosynthesis evolved several times independently in different plant families including monocots and dicots. Besides changes in carbon fixation, C4 plants have also evolved several alterations in nitrogen and sulfur nutrition, leading to better nitrogen use efficiency. Here, we utilized C3 and C4 species from 2 model systems, Flaveria and Panicum, to ask whether the evolution of C4 photosynthesis also affected phosphate homeostasis. The accumulation of phosphate within the plant shifted from the roots to the shoots with the evolution of C4, which can probably be explained by the higher demand of phosphate for completing the C4 cycle. A limitation of carbon assimilation by phosphate availability was shown solely for the C4 dicot plant, indicating a higher sensitivity to starvation. Metabolic responses to phosphate limitation, including accumulation of amino acids, TCA cycle intermediates, and starch, were genus or species specific, rather than associated with the photosynthesis type. The expression of key phosphate starvation response genes was induced in all species by phosphate deficiency, while the high induction of microRNA399 coupled with a repression of PHOSPHATE 2 (PHO2) was especially prominent in the C4 monocot. Thus, it seems that C4 photosynthesis increases the demand for phosphate in the leaves and C4 plants either respond more strongly to phosphate deficiency than C3 plants or experience inhibition of photosynthesis.
C4光合作用将二氧化碳集中在羧化酶周围，从而减少光呼吸并提高生产力。C4光合作用在包括单子叶植物和双子叶植物在内的不同植物科中独立进化了几次。除了碳固定的变化外，C4植物在氮和硫营养方面也发生了一些改变，从而提高了氮利用效率。在这里，我们利用来自黄顶菊属和黍属这两个模式系统的C3和C4物种，来探究C4光合作用的进化是否也影响了磷稳态。随着C4的进化，植物体内磷的积累从根部转移到了地上部，这可能是由于完成C4循环对磷的需求更高所致。仅在C4双子叶植物中显示了磷有效性对碳同化的限制，表明其对饥饿更敏感。对磷限制的代谢反应，包括氨基酸、三羧酸循环中间产物和淀粉的积累，是属或种特异性的，而不是与光合作用类型相关。所有物种中关键的磷饥饿反应基因的表达都受到磷缺乏的诱导，而在C4单子叶植物中，微小RNA399的高诱导以及对磷转运蛋白2（PHO2）的抑制尤为突出。因此，似乎C4光合作用增加了叶片对磷的需求，并且C4植物要么比C3植物对磷缺乏反应更强烈，要么经历光合作用的抑制。
