Potassium (K+) is an essential macronutrient for plant growth and development. Previous studies have demonstrated that Calcineurin B-Like Protein1 (CBL1) or CBL9 and CBL-Interacting Protein Kinase23 (CIPK23) regulate K+ uptake in Arabidopsis (Arabidopsis thaliana) roots by modulating K+ channel Arabidopsis K+ Transporter1. In this study, we show that the protein kinase CIPK9 interacts with the calcium sensor CBL3 and plays crucial roles in K+ homeostasis under low-K+ stress in Arabidopsis. Arabidopsis wild-type plants showed leaf chlorotic symptoms when grown for 10 d on low-K+ (100 μm) medium. Here, we show that plants lacking CIPK9 displayed a tolerant phenotype to low-K+ stress, which still maintained green leaves when the wild-type plants showed typical K+-deficient symptoms. Overexpressing lines of CIPK9 resulted in a low-K+-sensitive phenotype compared with wild-type plants. Furthermore, CBL2 and CBL3 were identified as upstream regulators of CIPK9. Both CBL2- and CBL3-overexpressing lines displayed similar low-K+-sensitive phenotypes and K+ contents to CIPK9-overexpressing lines. However, only cbl3 mutant plants, but not cbl2 mutant plants, showed the low-K+-tolerant phenotype similar to cipk9 mutants. Taken together, these results demonstrate that CIPK9 and CBL3 work together and function in K+ homeostasis under low-K+ stress in Arabidopsis.

Cytosolic Ca2+ in guard cells plays an important role in stomatal movement responses to environmental stimuli. These cytosolic Ca 2+ increases result from Ca 2+ influx through Ca 2+ -permeable channels in the plasma membrane and Ca 2+ release from intracellular organelles in guard cells. However, the genes encoding defined plasma membrane Ca 2+ -permeable channel activity remain unknown in guard cells and, with some exceptions, largely unknown in higher plant cells. Here, we report the identification of two Arabidopsis (Arabidopsis thaliana) cation channel genes, CNGC5 and CNGC6, that are highly expressed in guard cells. Cytosolic application of cyclic GMP (cGMP) and extracellularly applied membrane-permeable 8-Bromoguanosine 39,59-cyclic monophosphate-cGMP both activated hyperpolarization-induced inward-conducting currents in wild-type guard cells using Mg 2+ as the main charge carrier. The cGMP-activated currents were strongly blocked by lanthanum and gadolinium and also conducted Ba 2+ , Ca 2+, and Na + ions. cngc5 cngc6 double mutant guard cells exhibited dramatically impaired cGMP-activated currents. In contrast, mutations in CNGC1, CNGC2, and CNGC20 did not disrupt these cGMP-activated currents. The yellow fluorescent protein-CNGC5 and yellow fluorescent protein-CNGC6 proteins localize in the cell periphery. Cyclic AMP activated modest inward currents in both wild-type and cngc5cngc6 mutant guard cells. Moreover, cngc5 cngc6 double mutant guard cells exhibited functional abscisic acid (ABA)-activated hyperpolarization-dependent Ca 2+ -permeable cation channel currents, intact ABA-induced stomatal closing responses, and whole-plant stomatal conductance responses to darkness and changes in CO 2 concentration. Furthermore, cGMPactivated currents remained intact in the growth controlled by abscisic acid2 and abscisic acid insensitive1 mutants. This research demonstrates that the CNGC5 and CNGC6 genes encode unique cGMP-activated nonselective Ca 2+ -permeable cation channels in the plasma membrane of Arabidopsis guard cells.Plants lose water via transpiration and take in CO 2 for photosynthesis through stomatal pores. Each stomatal pore is surrounded by two guard cells, and stomatal movements are driven by the change of turgor pressure in guard cells. The intracellular second messenger Ca 2+ functions in guard cell signal transduction (Schroeder and

The phylogeny of Vitaceae was reconstructed sampling 114 accessions of Vitaceae and the outgroup Leea of Leeaceae, using three noncoding plastid markers: trnC-petN, trnH-psbA, and trnL-F. Six 5-merous genera including Parthenocissus, Yua, Ampelocissus, Vitis, Nothocissus, and Pterisanthes form a well-supported clade. Ampelopsis, Rhoicissus, and the Cissus striata complex form a clade sister to the clade containing all the other taxa of Vitaceae. The core Cissus clade is resolved to be sister to the Cayratia-Tetrastigma-Cyphostemma clade, forming a clade of taxa with 4-merous flowers. The Parthenocissus-Yua clade is sister to the Ampelocissus-Vitis-Nothocissus-Pterisanthes clade. The Old World Cissus is paraphyletic, with the New World core Cissus nested within it. The intercontinental disjunction between Africa and Asia may have evolved at least twice in Cissus. Cayratia is paraphyletic with four Asian species sampled grouping with Tetrastigma and the African species forming another clade.