Arabidopsis (Arabidopsis thaliana) leaf development relies on subsequent phases of cell proliferation and cell expansion. During the proliferation phase, chloroplasts need to divide extensively, and during the transition from cell proliferation to expansion, they differentiate into photosynthetically active chloroplasts, providing the plant with energy. The transcription factor GROWTH REGULATING FACTOR5 (GRF5) promotes the duration of the cell proliferation period during leaf development. Here, it is shown that GRF5 also stimulates chloroplast division, resulting in a higher chloroplast number per cell with a concomitant increase in chlorophyll levels in 35S:GRF5 leaves, which can sustain higher rates of photosynthesis. Moreover, 35S:GRF5 plants show delayed leaf senescence and are more tolerant for growth on nitrogen-depleted medium. Cytokinins also stimulate leaf growth in part by extending the cell proliferation phase, simultaneously delaying the onset of the cell expansion phase. In addition, cytokinins are known to be involved in chloroplast development, nitrogen signaling, and senescence. Evidence is provided that GRF5 and cytokinins synergistically enhance cell division and chlorophyll retention after dark-induced senescence, which suggests that they also cooperate to stimulate chloroplast division and nitrogen assimilation. Taken together with the increased leaf size, ectopic expression of GRF5 has great potential to improve plant productivity.

• MeSH
• Arabidopsis účinky léků   genetika   fyziologie   MeSH
• buněčné dělení účinky léků   MeSH
• chlorofyl metabolismus   MeSH
• chloroplasty účinky léků   metabolismus   ultrastruktura   MeSH
• cytokininy farmakologie   MeSH
• dusík nedostatek   MeSH
• fotosyntéza * účinky léků   MeSH
• geneticky modifikované rostliny MeSH
• listy rostlin účinky léků   růst a vývoj   fyziologie   ultrastruktura   MeSH
• proteiny 14-3-3 genetika   metabolismus   MeSH
• regulace genové exprese u rostlin účinky léků   MeSH
• rostlinné geny MeSH
• trans-aktivátory genetika   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

The phytohormone cytokinin has been shown to affect many aspects of plant development ranging from the regulation of the shoot apical meristem to leaf senescence. However, some studies have reported contradictory effects of cytokinin on leaf physiology. Therefore cytokinin treatments cause both chlorosis and increased greening and both lead to decrease or increase in cell size. To elucidate this multifaceted role of cytokinin in leaf development, we have employed a system of temporal controls over the cytokinin pool and investigated the consequences of modulated cytokinin levels in the third leaf of Arabidopsis. We show that, at the cell proliferation phase, cytokinin is needed to maintain cell proliferation by blocking the transition to cell expansion and the onset of photosynthesis. Transcriptome profiling revealed regulation by cytokinin of a gene suite previously shown to affect cell proliferation and expansion and thereby a molecular mechanism by which cytokinin modulates a molecular network underlying the cellular responses. During the cell expansion phase, cytokinin stimulates cell expansion and differentiation. Consequently, a cytokinin excess at the cell expansion phase results in an increased leaf and rosette size fueled by higher cell expansion rate, yielding higher shoot biomass. Proteome profiling revealed the stimulation of primary metabolism by cytokinin, in line with an increased sugar content that is expected to increase turgor pressure, representing the driving force of cell expansion. Therefore, the developmental timing of cytokinin content fluctuations, together with a tight control of primary metabolism, is a key factor mediating transitions from cell proliferation to cell expansion in leaves.

• MeSH
• Arabidopsis genetika   růst a vývoj   fyziologie   MeSH
• cytokininy metabolismus   MeSH
• genová ontologie MeSH
• listy rostlin genetika   růst a vývoj   fyziologie   MeSH
• proliferace buněk MeSH
• proteom * MeSH
• regulátory růstu rostlin metabolismus   MeSH
• signální transdukce * MeSH
• transkriptom * MeSH
• zvětšování buněk MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH

Maize is the highest yielding cereal crop grown worldwide for grain or silage. Here, we show that modulating the expression of the maize PLASTOCHRON1 (ZmPLA1) gene, encoding a cytochrome P450 (CYP78A1), results in increased organ growth, seedling vigour, stover biomass and seed yield. The engineered trait is robust as it improves yield in an inbred as well as in a panel of hybrids, at several locations and over multiple seasons in the field. Transcriptome studies, hormone measurements and the expression of the auxin responsive DR5rev:mRFPer marker suggest that PLA1 may function through an increase in auxin. Detailed analysis of growth over time demonstrates that PLA1 stimulates the duration of leaf elongation by maintaining dividing cells in a proliferative, undifferentiated state for a longer period of time. The prolonged duration of growth also compensates for growth rate reduction caused by abiotic stresses.

• MeSH
• biomasa * MeSH
• buněčné dělení genetika   MeSH
• časové faktory MeSH
• geneticky modifikované rostliny MeSH
• kukuřice setá genetika   růst a vývoj   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• listy rostlin genetika   růst a vývoj   metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• rostlinné proteiny genetika   MeSH
• semena rostlinná genetika   metabolismus   MeSH
• semenáček růst a vývoj   metabolismus   MeSH
• stanovení celkové genové exprese MeSH
• systém (enzymů) cytochromů P-450 genetika   MeSH
• vývojová regulace genové exprese MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH