Photosynthesis is among the first processes negatively affected by environmental cues and its performance directly determines plant cell fitness and ultimately crop yield. Primarily sites of photosynthesis, chloroplasts are unique sites also for the biosynthesis of precursors of the growth regulator auxin and for sensing environmental stress, but their role in intracellular auxin homeostasis, vital for plant growth and survival in changing environments, remains poorly understood. Here, we identified two ATP-binding cassette (ABC) subfamily B transporters, ABCB28 and ABCB29, which export auxin across the chloroplast envelope to the cytosol in a concerted action in vivo. Moreover, we provide evidence for an auxin biosynthesis pathway in Arabidopsis thaliana chloroplasts. The overexpression of ABCB28 and ABCB29 influenced stomatal regulation and resulted in significantly improved water use efficiency and survival rates during salt and drought stresses. Our results suggest that chloroplast auxin production and transport contribute to stomata regulation for conserving water upon salt stress. ABCB28 and ABCB29 integrate photosynthesis and auxin signals and as such hold great potential to improve the adaptation potential of crops to environmental cues.

• Klíčová slova
• ABC transporter, auxin, drought, hormone transport, photosynthesis, salinity, stress,
• Publikační typ
• časopisecké články MeSH

Plant hormones are master regulators of plant growth and development. Better knowledge of their spatial signaling and homeostasis (transport and metabolism) on the lowest structural levels (cellular and subcellular) is therefore crucial to a better understanding of developmental processes in plants. Recent progress in phytohormone analysis at the cellular and subcellular levels has greatly improved the effectiveness of isolation protocols and the sensitivity of analytical methods. This review is mainly focused on homeostasis of two plant hormone groups, auxins and cytokinins. It will summarize and discuss their tissue- and cell-type specific distributions at the cellular and subcellular levels.

• Klíčová slova
• auxin, cellular level, cytokinin, phytohormone metabolism, phytohormone transport, subcellular level,
• MeSH
• biologický transport MeSH
• cytokininy metabolismus   MeSH
• fyziologie rostlin * MeSH
• homeostáza * MeSH
• intracelulární prostor metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• metabolické sítě a dráhy MeSH
• organely metabolismus   MeSH
• regulátory růstu rostlin metabolismus   MeSH
• rostlinné buňky metabolismus   MeSH
• vývoj rostlin * MeSH
• Publikační typ
• časopisecké články MeSH
• přehledy MeSH
• Názvy látek
• cytokininy MeSH
• kyseliny indoloctové MeSH
• regulátory růstu rostlin MeSH

There have been few examples of the application of our growing knowledge of hormone action to crop improvement. In this review we discuss what is known about the critical points regulating auxin action. We examine auxin metabolism, transport, perception and signalling and identify genes and proteins that might be keys to regulation, particularly the rate-limiting steps in various pathways. Certain mutants show that substrate flow in biosynthesis can be limiting. To date there is little information available on the genes and proteins of catabolism. There have been several auxin transport proteins and some elegant transport physiology described recently, and the potential for using transport proteins to manage free indole-3-acetic acid (IAA) concentrations is discussed. Free IAA is very mobile, and so while it may be more practical to control auxin action through managing the receptor and signalling pathways, the candidate genes and proteins through which this can be done remain largely unknown. From the available evidence, it is clear that the reason for so few commercial applications arising from the control of auxin action is that knowledge is still limited.

• MeSH
• biologický transport MeSH
• homeostáza MeSH
• kyseliny indoloctové biosyntéza   metabolismus   MeSH
• rostliny genetika   metabolismus   MeSH
• signální transdukce fyziologie   MeSH
• vývoj rostlin MeSH
• vývojová regulace genové exprese MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• přehledy MeSH
• Názvy látek
• kyseliny indoloctové MeSH