Integrative Roles of Phytohormones on Cell Proliferation, Elongation and Differentiation in the Arabidopsis thaliana Primary Root

Abstract

The growth of multicellular organisms relies on cell proliferation, elongation and differentiation that are tightly regulated throughout development by internal and external stimuli. The plasticity of a growth response largely depends on the capacity of the organism to adjust the ratio between cell proliferation and cell differentiation. The primary root of Arabidopsis thaliana offers many advantages toward understanding growth homeostasis as root cells are continuously produced and move from cell proliferation to elongation and differentiation that are processes spatially separated and could be studied along the longitudinal axis. Hormones fine tune plant growth responses and a huge amount of information has been recently generated on the role of these compounds in Arabidopsis primary root development. In this review, we summarized the participation of nine hormones in the regulation of the different zones and domains of the Arabidopsis primary root. In some cases, we found synergism between hormones that function either positively or negatively in proliferation, elongation or differentiation. Intriguingly, there are other cases where the interaction between hormones exhibits unexpected results. Future analysis on the molecular mechanisms underlying crosstalk hormone action in specific zones and domains will unravel their coordination over PR development.

Thallusin Quantification in Marine Bacteria and Algae Cultures

“…Quantification of thallusin in growth media will help to address whether production is dependent on amino acids and less affected by carbon and nitrogen sources, as demonstrated by the indoleacetic acid (auxin) production of epiphytic bacteria on the red alga Pyropia yezoensis [39]. Land-plant-associated bacteria generally produce auxin, promoting cell division in root cells, similar to thallusin [40]. Ahmed and Hasnain (2010) detected elevated concentrations of auxin-86 µg L −1 (0.49 mmol L −1 )-in a Bacillus flexus culture shortly after the start of the stationary phase (48 h) [41], 10 7 -times higher than the thallusin concentrations at the same time point in the bacterial cultures.…”

It’s Time for a Change: The Role of Gibberellin in Root Meristem Development

“…SCR and SCL3 together with high levels of SHR protein inhibit MC formation, whereas low levels of SHR in the endodermis are required for activating CYCD6;1 expression in the endodermis. GAs antagonise SHR, SCR, and SCL3 activity regulating SHR abundance negatively acting on the SEUSS protein, an elicitor of SHR, SCR, and SCL3 transcription and promoting DELLA degradation, whose activity is required for SCL3 expression ( Paquette and Benfey, 2005 ; Heo et al, 2011 ; Bertolotti et al, 2021a ; Zluhan-Martínez et al, 2021 ).…”

ADA2b and GCN5 Affect Cytokinin Signaling by Modulating Histone Acetylation and Gene Expression during Root Growth of Arabidopsis thaliana

“…Between the meristematic zone and the elongation zone, there is a boundary, the transition zone (TZ), the position of which determines the meristem size [ 20 ]. The root cap consists of the columella (COL) and the lateral root cap (LRC), and its role stems to protect the epidermis and the SCN in the MZ [ 21 ]. COL cells are organized in cell files with large sizes departing from the columella stem cells (CSCs).…”