An Arabidopsis mutant deficient in phosphatidylinositol-4-phosphate kinases ß1 and ß2 displays altered auxin-related responses in roots

Abstract

Phosphatidylinositol 4-kinases (PI4Ks) are the first enzymes that commit phosphatidylinositol into the phosphoinositide pathway. Here, we show that Arabidopsis thaliana seedlings deficient in PI4Kβ1 and β2 have several developmental defects including shorter roots and unfinished cytokinesis. The pi4kβ1β2 double mutant was insensitive to exogenous auxin concerning inhibition of root length and cell elongation; it also responded more slowly to gravistimulation. The pi4kß1ß2 root transcriptome displayed some similarities to a wild type plant response to auxin. Yet, not all the genes displayed such a constitutive auxin-like response. Besides, most assessed genes did not respond to exogenous auxin. This is consistent with data with the transcriptional reporter DR5-GUS. The content of bioactive auxin in the pi4kß1ß2 roots was similar to that in wild-type ones. Yet, an enhanced auxin-conjugating activity was detected and the auxin level reporter DII-VENUS did not respond to exogenous auxin in pi4kß1ß2 mutant. The mutant exhibited altered subcellular trafficking behavior including the trapping of PIN-FORMED 2 protein in rapidly moving vesicles. Bigger and less fragmented vacuoles were observed in pi4kß1ß2 roots when compared to the wild type. Furthermore, the actin filament web of the pi4kß1ß2 double mutant was less dense than in wild-type seedling roots, and less prone to rebuilding after treatment with latrunculin B. A mechanistic model is proposed in which an altered PI4K activity leads to actin filament disorganization, changes in vesicle trafficking, and altered auxin homeostasis and response resulting in a pleiotropic root phenotypes.

Genome‐wide association study and network analysis of in vitro transformation in Populus trichocarpa support key roles of diverse phytohormone pathways and cross talk

“…Among these, 79 were differentially expressed in pi‐4kβ1, 2 mutants, 183 implicated as being regulated by WUS , HAN and/or GRF1 via differential expression and/or promoter binding, and 62 appear in the region of overlap as being regulated by WUS / HAN / GRF1 and the P14Kβ family (Fig. 6; Zhang et al ., 2013; Ma et al ., 2019; Piya et al ., 2020; Starodubtseva et al ., 2022). RWR scores were computed with WUS as a seed node and displayed two clusters, where genes in the cluster with greater scores have direct connections to WUS and others do not (Fig.…”

“…PI‐4Kβ1 (homolog of Potri.007G109000) is believed to affect SA (Janda et al ., 2014; Šašek et al ., 2014) via biosynthesis of phosphoinositides, which function as cofactors for enzymes involved in membranes and vesicles responsible in part for signaling molecule transport (Mayinger, 2012; Starodubtseva et al ., 2022). In addition to regulating levels of SA itself, phosphoinositides may regulate the action of downstream SA‐signaling genes, which are highly represented among targets of the phosphoinositide‐dependent phospholipase C (Kalachova et al ., 2015).…”

“…In addition to regulating levels of SA itself, phosphoinositides may regulate the action of downstream SA‐signaling genes, which are highly represented among targets of the phosphoinositide‐dependent phospholipase C (Kalachova et al ., 2015). Double loss‐of‐function mutants of PI‐4Kβ1 and the related PI‐4Kβ2 ( pi‐4kβ1, 2 ) show phenotypes including overaccumulation of SA (Janda et al ., 2014; Šašek et al ., 2014) and insensitivity to exogenous auxin (Starodubtseva et al ., 2022). Our epistasis results support four interactions for PI‐4Kβ1 , including with two uncharacterized genes, an elongation factor and the phosphate scavenger PURPLE ACID PHOSPATASE 12 (Hurley et al ., 2010; Robinson et al ., 2012) (Fig.…”

Phospholipid Signaling in Crop Plants: A Field to Explore

“…The production and accumulation of PI-4,5-P 2 is a characteristic of the plant response to salicylic acid [ 99 ]. Conversely, Arabidopsis plants mutated in some PI4Ks constitutively accumulate SA [ 100 ], while displaying altered auxin-related responses independently of SA accumulation [ 101 , 102 ].…”

Signal Peptide Peptidase and PI4Kβ1/2 play opposite roles in plant ER stress response and immunity

“…pi4kβ1,2 plants display autoimmunity-associated dwarfism and enhanced resistance against bacterial and oomycete pathogens (Janda et al 2014 ; Šašek et al 2014 ; Antignani et al 2015 ; Thulasi Devendrakumar et al 2023 ). In addition to displaying autoimmunity and dwarfism, pi4kβ1,2 seedlings also grow shorter roots with abnormal root hairs (Preuss et al 2006 ; Šašek et al 2014 ; Starodubtseva et al 2022 ; Thulasi Devendrakumar et al 2023 ). Through reverse genetic analysis it has been shown that the defense hormone salicylic acid (SA) and Enhanced Disease Susceptibility 1 ( EDS1 ), a central component required for ETI, are both contributing to pi4kβ1,2 ’s autoimmunity (Šašek et al 2014 ).…”