CRK5 Protein Kinase Contributes to the Progression of Embryogenesis of Arabidopsis thaliana

Abstract

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.

The Arabidopsis RLCK VI_A2 Kinase Controls Seedling and Plant Growth in Parallel with Gibberellin

“…Epibrassinolid (1 μM; E1641 Sigma) or Ethrel (100 μM; Bayer CropSience, Gent, Belgium) or GA 3 (20 µM; G7645 Sigma) were included into the medium from the beginning of culture. Hormone concentrations not inhibiting hypocotyl elongation were selected based on previous studies [ 50 , 51 , 52 , 53 ]. Transgenic RNAi seedlings and corresponding controls were grown in the presence of 5 µM β estradiol in addition to the hormones.…”

“…The oligonucleotide primers are listed in Supplemental Table S7 . A few of them have been previously published in [ 53 ]. qRT-PCR reactions were performed using an ABI PRISM 7700 sequence detection system (Thermo Fisher Scientific) and the qPCRBIO SyGreen Mix Hi-ROX master mix (PCR Biosystems Ltd., London, UK) using standard protocol (denaturation 95 °C for 10 min, 40 cycles of 95 °C for 10 s, and 62 °C for 60 s).…”

The AtCRK5 Protein Kinase Is Required to Maintain the ROS NO Balance Affecting the PIN2-Mediated Root Gravitropic Response in Arabidopsis

“…T-DNA insertion in any of the AtCRK genes was shown to delay the gravitropic responses of roots as well as hypocotyls [ 34 , 37 ]. The role of the AtCRK5 protein kinase was studied in more detail in our laboratory [ 34 , 35 , 37 , 38 ]. The AtCRK5 protein kinase is active in most Arabidopsis organs [ 35 ].…”

Do Plasmodesmata Play a Prominent Role in Regulation of Auxin-Dependent Genes at Early Stages of Embryogenesis?

“…On the contrary, before embryos reach the 16-cell stage, similar auxin concentrations are considered in all cells of the embryo proper due to nonpolar distribution of auxin efflux carriers [ 14 , 15 ]. Expression of the auxin-responsive DORNRÖSCHEN ( DRN ) gene [ 6 , 16 ] and activation of the DR5 promoter [ 8 ] in each cell of the embryo proper may support a homogenous auxin dispersion.…”