Phosphatidylinositol 3-Kinase Promotes V-ATPase Activation and Vacuolar Acidification and Delays Methyl Jasmonate-Induced Leaf Senescence

Abstract

(J.L., Y.J., J.Z., D. X.).PI3K and its product PI3P are both involved in plant development and stress responses. In this study, the down-regulation of PI3K activity accelerated leaf senescence induced by methyl jasmonate (MeJA) and suppressed the activation of vacuolar H + -ATPase (V-ATPase). Yeast two-hybrid analyses indicated that PI3K bound to the V-ATPase B subunit (VHA-B). Analysis of bimolecular fluorescence complementation in tobacco guard cells showed that PI3K interacted with VHA-B2 in the tonoplasts. Through the use of pharmacological and genetic tools, we found that PI3K and V-ATPase promoted vacuolar acidification and stomatal closure during leaf senescence. Vacuolar acidification was suppressed by the PIKfyve inhibitor in 35S:AtVPS34-YFP Arabidopsis during MeJA-induced leaf senescence, but the decrease was lower than that in YFP-labeled Arabidopsis. These results suggest that PI3K promotes V-ATPase activation and consequently induces vacuolar acidification and stomatal closure, thereby delaying MeJA-induced leaf senescence.

Phosphoinositide 3-Kinase Promotes Oxidative Burst, Stomatal Closure and Plant Immunity in Bacterial Invasion

“…Despite many reports, the role of PI3K is still not entirely clear besides its role in HR. For example, PI3K/ AtVPS34 functions in stomatal closure in plant stress response (Jung et al, 2002;Park et al, 2003;Choi et al, 2008;Liu et al, 2016), indicating a possible role of PI3K/AtVPS34 in stomatal immunity.…”

“…In this study, two types of bacteria, Pseudomonas syringae pv Tomato DC3000 (Pst DC3000) and avirulent Pst DC3000 (avrRpt2), were used. To examine the novel role of PI3K in plant immunity, AtVPS34 overexpressing Arabidopsis and two PI3K inhibitors, LY294002 (LY) and wortmannin (WM), were used as previously described (Liu et al, 2016). LY, which is derived from the flavonoid quercetin, competes with ATP and binds to Lys residues in the ATP-binding pocket of PI3Ks (Walker et al, 2000).…”

A pivotal role of phosphatidylinositol 3-kinase in delaying of methyl jasmonate-induced leaf senescence

“…The inhibition of PI3K or V-ATPase activity leads to the early senescence. 6 However, PI3K also exhibited diverse functions in plant development and stress response, such as actin filament reorganization, plasma membrane endocytosis, and NADPH oxidase activation. [11][12][13] Hence, it may be involved in the regulation of leaf senescence.…”

“…Additionally, stomatal opening was enhanced compared with that under control conditions, when treated senescent leaves induced by MeJA with the V-ATPase inhibitor Bafilomycin A1 (BFA1) to accelerate vacuolar alkalization. 6 However, another type of proton pump, vacuolar H C -pyrophosphatases (V-PPases) cannot be ignored. V-PPases are single-subunit homodimers that also generate proton gradients in endomembrane compartments by using pyrophosphate (PPi) other than ATP.…”

“…Our data determined that PI3K also bind with V-ATPase subunit in plant. 6 Additionally, BiFC experiment was further conducted using onion epidermal cells to prove the interaction of PI3K with the V-ATPase subunit B2 on tonoplast. Tonoplast localization was achieved by fusing the coding region of the mCherry to the C-terminus of g-TIP (VACmCherry), an aquaporin of the vacuolar membrane.…”