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Friday Seminar by Mr. Lokesh Saini


GKP Lab/ Friday/ March 13, 2020/ 3.30 pm/ SAUR-PP2C.D-mediated regulation of cell expansion throughmodulation of plasma membrane H+ATPase activity.
Category: Research
Posted by: bedineel

 

SAUR-PP2C.D-mediated regulation of cell expansion throughmodulation of Plasma membrane H+-ATPase activity’

Lokesh Saini

 

The phytohormone auxin promotes plant shoot growth by regulating fundamental processes of cell division, expansion and differentiation. After auxin perception and signalling, early auxin responsive genes are induced within minutes. These include AUX/IAAs, GRETCHEN HAGEN3s (GH3s), and SMALL AUXIN UP RNAs (SAURs). Expression of AUX/IAAs and GH3s attenuate the auxin signalling through feedback regulation. Induction of SAURs has been proposed to promote cell expansion. In Arabidopsis, plant specific SAUR family comprises of 81 members. Most of the SAUR genes are auxin -inducible. SAUR19 has been found to regulate cell expansion, including increased hypocotyl and leaf size and altered tropic responses. The papers presented here delineate the mechanism of auxin -mediated cell expansion and plant growth. First study suggests that auxin-induced SAURs activate plasma membrane H+-ATPases to promote cell expansion via an acid growth mechanism.  Overexpression of SAUR19 exhibits increased H+-ATPases activity which leads to the reduction in apoplastic pH and hyperpolarization of plasma membrane. SAUR proteins promote PM H+-ATPases activation by inhibiting D-clade type 2C Protein phosphatases (PP2C.Ds), which can reduce the activity of PM H+-ATPases by dephosphorylation at Thr-947. Second report explains how SAURs bind to PP2C.D protein and inhibit phosphatase activity. Here, they have identified a conserved motif near the catalytic domain, which is required for SAUR binding in Arabidopsis. Results show that mutation in this motif abolishes the SAUR binding but has no effect on catalytic activity. In planta expression of SAUR-immune pp2c.d2 and pp2c.d5 showed severe cell expansion defects and reduced activity of PM H+-ATPase. Together these studies, revealed a SAUR-PP2C.D regulation of cell expansion via modulation of PM H+-ATPase activity.
 

References:

Spartz, A.K., Ren, H., Park, M.Y., Grandt, K.N., Lee, S.H., Murphy, A.S., Sussman, M.R., Overvoorde, P.J., and Gray, W.M. (2014). SAUR inhibition of PP2C-D phosphatases activates plasma membrane H+-ATPases to promote cell expansion in Arabidopsis. Plant Cell 26: 2129–2142.

Wong, J.H., Spartz, A.K., Park, M.Y., Du, M., and Gray, W.M. (2019). Mutation of a Conserved Motif of PP2C.D Phosphatases Confers SAUR Immunity and Constitutive Activity. Plant Physiol. 181: 353–366.