rapid alkalinization factor 1 (AtRALF1) is a small secreted peptide hormone that inhibits root growth by repressing cell expansion. Although it is known that AtRALF1 binds the plasma membrane receptor FERONIA and conveys its signals via phosphorylation, the AtRALF1 signaling pathway is largely unknown. Here, using a yeast two-hybrid system to search for AtRALF1-interacting proteins in , we identified calmodulin-like protein 38 (CML38) as an AtRALF1-interacting partner. We also found that CML38 and AtRALF1 are both secreted proteins that physically interact in a Ca- and pH-dependent manner. CML38-knockout mutants generated via T-DNA insertion were insensitive to AtRALF1, and simultaneous treatment with both AtRALF1 and CML38 proteins restored sensitivity in these mutants. Hybrid plants lacking CML38 and having high accumulation of the AtRALF1 peptide did not exhibit the characteristic short-root phenotype caused by overexpression. Although CML38 was essential for AtRALF1-mediated root inhibition, it appeared not to have an effect on the AtRALF1-induced alkalinization response. Moreover, acridinium-labeling of AtRALF1 indicated that the binding of AtRALF1 to intact roots is CML38-dependent. In summary, we describe a new component of the AtRALF1 response pathway. The new component is a calmodulin-like protein that binds AtRALF1, is essential for root growth inhibition, and has no role in AtRALF1 alkalinization.

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Bamboo species are an alternative for the composition of forest plantations. However, their potential has not been explored due to the hard time in producing large-scale clonal plants. Thus, the aim this work was to evaluate the in vitro establishment, bud multiplication and ex vitro rooting of Bambusa vulgaris. The first experiment tested different systemic and contact fungicide solutions, based on exposure time, during the establishment phase. Established explants were subjected to evaluation of residual fungicide effect on subcultures during the multiplication and elongation phases. The second experiment evaluated the influence of activated carbon on ex vitro survival and on adventitious rooting. Explant immersion in liquid culture medium added with 1.0 mL of fungicide for 120 hours has favored the in vitro establishment and reduced fungal contamination. On the other hand, it favored the shoot emission of shoots per explant during the multiplication phase. Both rooting induction culture medium and mini-incubator system use were effective in enabling adventitious root formation. The presence of activated carbon in the rooting induction culture medium resulted in a higher clonal plant survival rate.

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