ATL8, a RING E3 ligase, modulates root growth and phosphate homeostasis in Arabidopsis

Ubiquitination-mediated post-translational modification of proteins is a pivotal regulatory mechanism involved in the growth and development of the plant. The Arabidopsis T ' oxicos en Levadura (ATL) family is a group of RING-type ubiquitin ligases (E3) and ATL8 is a membrane-localized protein. Here, a reverse genetics approach was used to elucidate the role of ATL8 in phosphate (Pi) homeostasis. Deficiencies of Pi and sucrose (Suc) enhanced the relative expression level of ATL8 in different tissues of the wild-type (Wt). The relative expression level of ATL8 was attenuated and augmented in the mutant (atl8) and overexpression lines (Oe1 and Oe2), respectively. There were significant reductions in different root traits, root hairs, root to shoot ratio, and total Pi content in atl8 compared with the Wt under different Pi regimes. On the contrary, Oe1 and Oe2 lines exhibited enhancement in some of these traits. Noticeably, anthocyanin content was significantly reduced in Oe1 and Oe2 compared with the Wt and atl8 under P-condition. Abscisic acid (ABA) treatment led to an increase in the primary root length of atl8 compared with the Wt, suggesting a cross-talk between ABA and ATL8 on root growth. Furthermore, the relative expression levels of the genes involved in the maintenance of Pi homeostasis (WRKY75, RNS1, E3L, and ACP5) were differentially modulated in atl8, Oe1, and Oe2 compared with the Wt under different Pi regimes. The results revealed the pivotal role of ATL8 in mediating morphophysiological and molecular adaptive responses to Pi deficiency.

Automated summary

Ubiquitination-mediated post-translational modification of proteins is a crucial mechanism in plant growth and development. This study found that ATL8 plays a pivotal role in phosphate homeostasis, and its relative expression level is influenced by phosphate and sucrose deficiency. The mutant atl8 showed significant reductions in root traits, root to shoot ratio, and total phosphate content compared to the wild-type under different phosphate regimes. In contrast, the overexpression lines Oe1 and Oe2 exhibited enhancements in some of these traits. Furthermore, ABA and ATL8 were shown to have a cross-talk on root growth and modulate the expression levels of genes involved in phosphate homeostasis.