Genetius

The study investigates how auxin regulates root cell elongation in Arabidopsis thaliana by modulating the transcription of pectin‑degrading polygalacturonases (PGRAs). Auxin down‑regulates PGRA1 expression to limit pectin remodeling, and mutants lacking PGRAs fail to enhance root growth when auxin levels are reduced, linking auxin signaling to cell‑wall modification.

The study reveals that cross‑talk between the ERECTA receptor pathway and auxin signaling determines the output of bilateral stem cell layers during secondary growth by phosphorylating the transcription factor AINTEGUMENTA (ANT). Phosphorylation of ANT biases stem cell activity toward the production of a single vascular cell type, thereby modulating root girth and overall biomass accumulation.

The study identifies TOW as a critical component linking intracellular auxin signaling to cell surface perception, thereby regulating PIN transporter polarity and trafficking during auxin canalization. tow mutants show impaired vascular regeneration and defective PIN polarization, with TOW localizing to Golgi, TGN, and plasma membrane and interacting with TMK1 and the CAMEL-CANAR complex. These findings elucidate how auxin signaling coordinates directional transport for flexible vasculature formation.

The study applied a CRISPR/Cas9 multiplex guide RNA strategy to delete entire open reading frames of four reproductive genes in Arabidopsis thaliana, achieving homozygous deletions already in the T1 generation with rates of 8.3–30%. Deletion efficiencies correlated with DeepSpCas9 prediction scores, and phenotypic analyses revealed unexpected effects of residual gene fragments on fertilization and seed development.

The study investigates the Arabidopsis ribosomal protein RPS6A and its role in auxin‑related root growth, revealing that rps6a mutants display shortened primary roots, fewer lateral roots, and defective vasculature that are not rescued by exogenous auxin. Cell biological observations and global transcriptome profiling show weakened auxin signaling and reduced levels of PIN auxin transporters in the mutant, indicating a non‑canonical function of the ribosomal subunit in auxin pathways.

The study reveals that auxin signaling via the cell‑surface ABP1‑TMK1 receptor complex directly phosphorylates and stabilizes the PIN2 auxin transporter, reinforcing asymmetric auxin flow during root gravitropism. Autophosphorylation of TMK1 after gravistimulation promotes its interaction with PIN2, and ABP1 functions redundantly with ABL3 upstream of TMK1, establishing a positive feedback loop essential for robust root bending.

The study shows that the Hyaloperonospora arabidopsidis effector HaRxL106 interferes with the Arabidopsis AUX/IAA protein IAA11, weakening its repressive role and thereby enhancing auxin signaling, which triggers shade‑avoidance‑like growth and concomitantly dampens immune responses. These results reveal a mechanism by which a pathogen effector co‑opts hormonal pathways to promote infection.