A subset of plasma membrane-localized PP2C.D phosphatases negatively regulate SAUR-mediated cell expansion in Arabidopsis

Abstract

The plant hormone auxin regulates numerous growth and developmental processes throughout the plant life cycle. One major function of auxin in plant growth and development is the regulation of cell expansion. Our previous studies have shown that SMALL AUXIN UP RNA (SAUR) proteins promote auxin-induced cell expansion via an acid growth mechanism. These proteins inhibit the PP2C.D family phosphatases to activate plasma membrane (PM) H+-ATPases and thereby promote cell expansion. However, the functions of individual PP2C.D phosphatases are poorly understood. Here, we investigated PP2C.D-mediated control of cell expansion and other aspects of plant growth and development. The nine PP2C.D family members exhibit distinct subcellular localization patterns. Our genetic findings demonstrate that the three plasma membrane-localized members, PP2C.D2, PP2C.D5, and PP2C.D6, are the major regulators of cell expansion. These phosphatases physically interact with SAUR19 and PM H+-ATPases, and inhibit cell expansion by dephosphorylating the penultimate threonine of PM H+-ATPases. PP2C.D genes are broadly expressed and are crucial for diverse plant growth and developmental processes, including apical hook development, phototropism, and organ growth. GFP-SAUR19 overexpression suppresses the growth defects conferred by PP2C.D5 overexpression, indicating that SAUR proteins antagonize the growth inhibition conferred by the plasma membrane-localized PP2C.D phosphatases. Auxin and high temperature upregulate the expression of some PP2C.D family members, which may provide an additional layer of regulation to prevent plant overgrowth. Our findings provide novel insights into auxin-induced cell expansion, and provide crucial loss-of-function genetic support for SAUR-PP2C.D regulatory modules controlling key aspects of plant growth.

Natural variations of growth thermo‐responsiveness determined by SAUR26/27/28 proteins in Arabidopsis thaliana

“…The SAUR26 subfamily proteins also connect with PP2C‐D that are major regulators in auxin‐regulated cell expansion (Ren et al ., ). SAUR26 and SAUR27 could physically interact with PP2C‐D5 and PP2C‐D6, as indicated by a series of protein–protein interaction assays (Figs c, S7b), and overexpressing these SAUR proteins leads to higher activity of PM H + ‐ATPase (Fig.…”

Auxin-Abscisic Acid Interactions in Plant Growth and Development

“…PP2C.D family members that target AHA2 [74], effectively repressing their activity and leading to elevated AHA2 phosphorylation activation (Figure 3). For further reading in this area please see references [75][76][77]. Treatment of either light-grown or dark-grown seedlings with ABA results in inhibition of hypocotyl elongation [48].…”

Differentially expressed genes and phenotypic variation in florets among the isogenic Ogura-CMS, DGMS and inbred lines of broccoli

“…D5 derivatives confer severe cell expansion defects and correspondingly cause constitutively low levels of PM H + -ATPase phosphorylation. It has been proven that PM H + -ATPase plays an important role in seed germination due to its role in supplying cell walls with the H + -ions necessary for cell elongation commencement in embryos, but the mechanism of PM H + -ATPase activation in germinating seeds has not been determined [34,35]. With regard to ET metabolism, high expression of the ERF1/2 gene is involved in fruit ripening, and overexpression of this gene has been found to be speci cally induced by glucose during germination and early seedling development in Arabidopsis plants [36].…”