The fine tuning of hormone (e.g., auxin and gibberellin) levels and hormone signaling is required for maintaining normal embryogenesis. Embryo polarity, for example, is ensured by the directional movement of auxin that is controlled by various types of auxin transporters. Here, we present pieces of evidence for the auxin-gibberellic acid (GA) hormonal crosstalk during embryo development and the regulatory role of the Arabidopsis thaliana Calcium-Dependent Protein Kinase-Related Kinase 5 (AtCRK5) in this regard. It is pointed out that the embryogenesis of the Atcrk5-1 mutant is delayed in comparison to the wild type. This delay is accompanied with a decrease in the levels of GA and auxin, as well as the abundance of the polar auxin transport (PAT) proteins PIN1, PIN4, and PIN7 in the mutant embryos. We have previously showed that AtCRK5 can regulate the PIN2 and PIN3 proteins either directly by phosphorylation or indirectly affecting the GA level during the root gravitropic and hypocotyl hook bending responses. In this manuscript, we provide evidence that the AtCRK5 protein kinase can in vitro phosphorylate the hydrophilic loops of additional PIN proteins that are important for embryogenesis. We propose that AtCRK5 can govern embryo development in Arabidopsis through the fine tuning of auxin-GA level and the accumulation of certain polar auxin transport proteins.

• Klíčová slova
• Arabidopsis thaliana, Calcium-Dependent Protein Kinase-Related Kinase (CRK), GA3, auxin gradient, embryogenesis, polar auxin transport (PAT) proteins,
• MeSH
• Arabidopsis růst a vývoj   metabolismus   MeSH
• ELISA MeSH
• gibereliny analýza   metabolismus   MeSH
• klíčení * MeSH
• kyseliny indoloctové metabolismus   MeSH
• membránové transportní proteiny genetika   metabolismus   MeSH
• protein-serin-threoninkinasy metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• receptory buněčného povrchu metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• semena rostlinná anatomie a histologie   růst a vývoj   metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• CRK5 protein, Arabidopsis MeSH Prohlížeč
• gibberellic acid MeSH Prohlížeč
• gibereliny MeSH
• kyseliny indoloctové MeSH
• membránové transportní proteiny MeSH
• protein-serin-threoninkinasy MeSH
• proteiny huseníčku MeSH
• receptory buněčného povrchu MeSH

Redirection of intercellular auxin fluxes via relocalization of the PIN-FORMED 3 (PIN3) and PIN7 auxin efflux carriers has been suggested to be necessary for the root gravitropic response. Cytokinins have also been proposed to play a role in controlling root gravitropism, but conclusive evidence is lacking. We present a detailed study of the dynamics of root bending early after gravistimulation, which revealed a delayed gravitropic response in transgenic lines with depleted endogenous cytokinins (Pro35S:AtCKX) and cytokinin signaling mutants. Pro35S:AtCKX lines, as well as a cytokinin receptor mutant ahk3, showed aberrations in the auxin response distribution in columella cells consistent with defects in the auxin transport machinery. Using in vivo real-time imaging of PIN3-GFP and PIN7-GFP in AtCKX3 overexpression and ahk3 backgrounds, we observed wild-type-like relocalization of PIN proteins in the columella early after gravistimulation, with gravity-induced relocalization of PIN7 faster than that of PIN3. Nonetheless, the cellular distribution of PIN3 and PIN7 and expression of PIN7 and the auxin influx carrier AUX1 was affected in AtCKX overexpression lines. Based on the retained cytokinin sensitivity in pin3 pin4 pin7 mutant, we propose the AUX1-mediated auxin transport rather than columella-located PIN proteins as a target of endogenous cytokinins in the control of root gravitropism.

• Klíčová slova
• AUX1, Arabidopsis, PIN-FORMED (PIN), auxin, cytokinins, root gravitropism,
• MeSH
• Arabidopsis účinky léků   fyziologie   MeSH
• biologické modely MeSH
• biologický transport účinky léků   MeSH
• cytokininy farmakologie   MeSH
• gravitace MeSH
• gravitropismus účinky léků   MeSH
• kořeny rostlin účinky léků   fyziologie   MeSH
• kyseliny indoloctové metabolismus   MeSH
• meristém účinky léků   fyziologie   MeSH
• proteiny huseníčku metabolismus   MeSH
• signální transdukce účinky léků   MeSH
• zelené fluorescenční proteiny metabolismus   MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• AUX1 protein, Arabidopsis MeSH Prohlížeč
• cytokininy MeSH
• kyseliny indoloctové MeSH
• proteiny huseníčku MeSH
• zelené fluorescenční proteiny MeSH

Aluminium (Al) stress is a major limiting factor for worldwide crop production in acid soils. In Arabidopsis thaliana, the TAA1-dependent local auxin biosynthesis in the root-apex transition zone (TZ), the major perception site for Al toxicity, is crucial for the Al-induced root-growth inhibition, while the mechanism underlying Al-regulated auxin accumulation in the TZ is not fully understood. In the present study, the role of auxin transport in Al-induced local auxin accumulation in the TZ and root-growth inhibition was investigated. Our results showed that PIN-FORMED (PIN) proteins such as PIN1, PIN3, PIN4 and PIN7 and AUX1/LAX proteins such as AUX1, LAX1 and LAX2 were all ectopically up-regulated in the root-apex TZ in response to Al stress and coordinately regulated local auxin accumulation in the TZ and root-growth inhibition. The ectopic up-regulation of PIN1 in the TZ under Al stress was regulated by both ethylene and auxin, with auxin signalling acting downstream of ethylene. Al-induced PIN1 up-regulation and auxin accumulation in the root-apex TZ was also regulated by the calossin-like protein BIG. Together, our results provide insight into how Al stress induces local auxin accumulation in the TZ and root-growth inhibition through the local regulation of auxin transport.

• Klíčová slova
• PIN1, aluminium, auxin transport, root growth, root-apex transition zone,
• MeSH
• Arabidopsis účinky léků   genetika   růst a vývoj   fyziologie   MeSH
• biologický transport MeSH
• ethyleny metabolismus   MeSH
• fyziologický stres MeSH
• hliník toxicita   MeSH
• kořeny rostlin účinky léků   genetika   růst a vývoj   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• membránové transportní proteiny genetika   metabolismus   MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• proteiny vázající kalmodulin genetika   metabolismus   MeSH
• regulace genové exprese u rostlin MeSH
• regulátory růstu rostlin metabolismus   MeSH
• upregulace MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• BIG protein, Arabidopsis MeSH Prohlížeč
• ethylene MeSH Prohlížeč
• ethyleny MeSH
• hliník MeSH
• kyseliny indoloctové MeSH
• membránové transportní proteiny MeSH
• PIN1 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku MeSH
• proteiny vázající kalmodulin MeSH
• regulátory růstu rostlin MeSH

Intercellular flow of the phytohormone auxin underpins multiple developmental processes in plants. Plant-specific pin-formed (PIN) proteins and several phosphoglycoprotein (PGP) transporters are crucial factors in auxin transport-related development, yet the molecular function of PINs remains unknown. Here, we show that PINs mediate auxin efflux from mammalian and yeast cells without needing additional plant-specific factors. Conditional gain-of-function alleles and quantitative measurements of auxin accumulation in Arabidopsis and tobacco cultured cells revealed that the action of PINs in auxin efflux is distinct from PGP, rate-limiting, specific to auxins, and sensitive to auxin transport inhibitors. This suggests a direct involvement of PINs in catalyzing cellular auxin efflux.

• MeSH
• ABC transportéry genetika   metabolismus   MeSH
• Arabidopsis cytologie   růst a vývoj   metabolismus   fyziologie   MeSH
• biologický transport MeSH
• buněčná membrána metabolismus   MeSH
• ftalimidy farmakologie   MeSH
• gravitropismus MeSH
• HeLa buňky MeSH
• kinetika MeSH
• kořeny rostlin fyziologie   MeSH
• kultivované buňky MeSH
• kyseliny indoloctové metabolismus   MeSH
• kyseliny naftalenoctové metabolismus   MeSH
• lidé MeSH
• membránové transportní proteiny genetika   metabolismus   MeSH
• mutace MeSH
• proteiny huseníčku genetika   metabolismus   MeSH
• Saccharomyces cerevisiae genetika   MeSH
• tabák MeSH
• transfekce MeSH
• transformace genetická MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Research Support, U.S. Gov't, Non-P.H.S. MeSH
• Názvy látek
• 1-naphthaleneacetic acid MeSH Prohlížeč
• ABC transportéry MeSH
• alpha-naphthylphthalamic acid MeSH Prohlížeč
• ATPGP1 protein, Arabidopsis MeSH Prohlížeč
• ftalimidy MeSH
• kyseliny indoloctové MeSH
• kyseliny naftalenoctové MeSH
• membránové transportní proteiny MeSH
• PIN1 protein, Arabidopsis MeSH Prohlížeč
• PIN2 protein, Arabidopsis MeSH Prohlížeč
• PIN4 protein, Arabidopsis MeSH Prohlížeč
• PIN7 protein, Arabidopsis MeSH Prohlížeč
• proteiny huseníčku MeSH

The plant hormone auxin and its directional transport are known to play a crucial role in defining the embryonic axis and subsequent development of the body plan. Although the role of PIN auxin efflux transporters has been clearly assigned during embryonic shoot and root specification, the role of the auxin influx carriers AUX1 and LIKE-AUX1 (LAX) proteins is not well established. Here, we used chemical and genetic tools on Brassica napus microspore-derived embryos and Arabidopsis thaliana zygotic embryos, and demonstrate that AUX1, LAX1 and LAX2 are required for both shoot and root pole formation, in concert with PIN efflux carriers. Furthermore, we uncovered a positive-feedback loop between MONOPTEROS (ARF5)-dependent auxin signalling and auxin transport. This MONOPTEROS-dependent transcriptional regulation of auxin influx (AUX1, LAX1 and LAX2) and auxin efflux (PIN1 and PIN4) carriers by MONOPTEROS helps to maintain proper auxin transport to the root tip. These results indicate that auxin-dependent cell specification during embryo development requires balanced auxin transport involving both influx and efflux mechanisms, and that this transport is maintained by a positive transcriptional feedback on auxin signalling.

• Klíčová slova
• AUX1, Arabidopsis thaliana embryogenesis, Auxin transport, Brassica napus, LIKE-AUX1 (LAX), MONOPTEROS (ARF5), Microspore, PIN,
• MeSH
• Arabidopsis embryologie   genetika   metabolismus   MeSH
• biologický transport genetika   fyziologie   MeSH
• Brassica napus embryologie   genetika   metabolismus   MeSH
• kyseliny indoloctové metabolismus   MeSH
• rostlinné proteiny metabolismus   MeSH
• semena rostlinná cytologie   metabolismus   MeSH
• signální transdukce genetika   fyziologie   MeSH
• Publikační typ
• časopisecké články MeSH
• práce podpořená grantem MeSH
• Názvy látek
• kyseliny indoloctové MeSH
• rostlinné proteiny MeSH