@article{22366,
  abstract     = {Gravitropism is a fundamental adaptive response in plants that enables directional growth to optimize resource acquisition. In this study, we employed forward genetic screening to identify Arabidopsis mutants with defective hypocotyl gravitropism and isolated the short and agravitropic hypocotyl in dark1 (sad1) mutant, which carries a point mutation (G110E) in the SAC1 gene encoding a phosphoinositide phosphatase. Deficiency of SAC1 disrupted gravity-induced polar localization of PIN3 in endodermal cells, impairing auxin redistribution and leading to hypocotyl gravitropism defects. Subcellular localization analysis revealed that SAC1 is partially localized to the PVC/tonoplast and participates in late endosomal trafficking. The sac1 mutation leads to abnormal vacuolar morphology, which is associated with defects in amyloplast sedimentation during the gravitropic response in Arabidopsis shoots. We further revealed that SAC1 interacts with GRV2, a key regulator of the late endocytic pathway, and that both proteins cooperatively regulate shoot gravitropism. In summary, this study identified SAC1 as a regulator of shoot gravitropism, revealing its important role in modulating vacuolar homeostasis, amyloplast sedimentation, PIN3 trafficking, and auxin distribution. These findings provide insights into the molecular mechanisms linking membrane transport to environmental adaptation in plants.},
  author       = {Sun, Lianghanxiao and Jia, Wenxin and Mao, Yanbo and Li, Xin and Kong, Mengjuan and She, Ji and Friml, Jiří and Tan, Shutang},
  issn         = {1365-313X},
  journal      = {The Plant Journal},
  keywords     = {auxin, SAC1, GRV2, PIN3, vacuole, gravitropism, Arabidopsis},
  number       = {1},
  publisher    = {Wiley},
  title        = {{Regulation of shoot gravitropism and branching angle by the GRV2-SAC1 axis in Arabidopsis}},
  doi          = {10.1111/tpj.71042},
  volume       = {127},
  year         = {2026},
}

@article{9986,
  abstract     = {Size control is a fundamental question in biology, showing incremental complexity in plants, whose cells possess a rigid cell wall. The phytohormone auxin is a vital growth regulator with central importance for differential growth control. Our results indicate that auxin-reliant growth programs affect the molecular complexity of xyloglucans, the major type of cell wall hemicellulose in eudicots. Auxin-dependent induction and repression of growth coincide with reduced and enhanced molecular complexity of xyloglucans, respectively. In agreement with a proposed function in growth control, genetic interference with xyloglucan side decorations distinctly modulates auxin-dependent differential growth rates. Our work proposes that auxin-dependent growth programs have a spatially defined effect on xyloglucan’s molecular structure, which in turn affects cell wall mechanics and specifies differential, gravitropic hypocotyl growth.},
  author       = {Velasquez, Silvia Melina and Guo, Xiaoyuan and Gallemi, Marçal and Aryal, Bibek and Venhuizen, Peter and Barbez, Elke and Dünser, Kai Alexander and Darino, Martin and Pӗnčík, Aleš and Novák, Ondřej and Kalyna, Maria and Mouille, Gregory and Benková, Eva and Bhalerao, Rishikesh P. and Mravec, Jozef and Kleine-Vehn, Jürgen},
  issn         = {1422-0067},
  journal      = {International Journal of Molecular Sciences},
  keywords     = {auxin, growth, cell wall, xyloglucans, hypocotyls, gravitropism},
  number       = {17},
  publisher    = {MDPI},
  title        = {{Xyloglucan remodeling defines auxin-dependent differential tissue expansion in plants}},
  doi          = {10.3390/ijms22179222},
  volume       = {22},
  year         = {2021},
}