Arabidopsis Inositol Polyphosphate 6-/3-Kinase (AtIpk2β) Is Involved in Axillary Shoot Branching via Auxin Signaling

Abstract

The Arabidopsis (Arabidopsis thaliana) inositol polyphosphate 6-/3-kinase gene (AtIpk2b) is known to participate in inositol phosphate metabolism. However, little is known about its physiological functions in higher plants. Here, we report that AtIpk2b regulates Arabidopsis axillary shoot branching. By overexpressing AtIpk2b in the wild type and mutants, we found that overexpression of AtIpk2b leads to more axillary shoot branches. Further analysis of AtIpk2b overexpression lines showed that axillary meristem forms earlier and the bud outgrowth rate is also accelerated, resulting in more axillary shoot branches. The AtIpk2b promoter/b-glucuronidase (GUS) fusion (AtIpk2bTGUS) expression pattern is similar to that of the auxin reporter DR5TGUS. Moreover, AtIpk2b can be induced in response to exogenous indole-3-acetic acid (IAA) treatments. In addition, AtIpk2b overexpression plants exhibit IAA-related phenotypes and are more resistant to exogenous IAA treatments. Further analysis employing reverse transcription-polymerase chain reaction shows that some genes, including auxin-biosynthesis (CYP83B1), auxin-transport (PIN4), and auxin-mediated branching genes (MAX4 and SPS), are regulated by AtIpk2b. Taken together, our data provide insights into a role for AtIpk2b in axillary shoot branching through the auxin signaling pathway.

TheRON1/FRY1/SAL1Gene Is Required for Leaf Morphogenesis and Venation Patterning in Arabidopsis

“…The increased branching of ron1-1 shoots, although clearly distinct from the severe effects of axr1 and hve mutations on inflorescence branching, may also result from a decrease in apical dominance due to defective auxin perception. In line with this idea, increased shoot branching has recently been described for plants that overexpress an inositol polyphosphate 6-/3-kinase gene (Zhang et al, 2007). Although our assays did not allow us to detect changes in sensitivity to 2,4-D, those authors found that these overexpressors are less sensitive to IAA than the wild type (Zhang et al, 2007).…”

“…In line with this idea, increased shoot branching has recently been described for plants that overexpress an inositol polyphosphate 6-/3-kinase gene (Zhang et al, 2007). Although our assays did not allow us to detect changes in sensitivity to 2,4-D, those authors found that these overexpressors are less sensitive to IAA than the wild type (Zhang et al, 2007). Alternatively, it is also possible that the effect of ron1 mutations on auxin responses results from a perturbation of auxin transport.…”

Identification of genes necessary for wild-type levels of seed phytic acid in Arabidopsis thaliana using a reverse genetics approach

“…In the case of AtIPK2a and AtIPK2b, both enzymes use Ins(1,4,5)P 3 as a substrate and display the same 6-/3-kinase activity that generates Ins(1,3,4,5,6)P 5 predominantly via Ins(1,4,5,6)P 4 intermediate (Stevenson-Paulik et al 2002;Xia et al 2003). However, loss-of-function studies have shown that AtIPK2a plays a role in pollen germination and root growth (Xu et al 2005), whereas AtIPK2b functions in axillary shoot branching through the auxin signaling pathway (Zhang et al 2007). With regard to seed phytic acid, atipk2b mutants exhibit an lpa phenotype while atipk2a mutants maintain wild-type levels of seed InsP 6 .…”

Arabidopsis phosphatidylinositol monophosphate 5-kinase 2 is involved in root gravitropism through regulation of polar auxin transport by affecting the cycling of PIN proteins

“…Although many pieces of evidence have indicated the crosstalk between the PI signaling pathway and auxin signaling pathway via regulation of auxin homeostasis or auxin transport [12,42,[49][50][51], the potential link of PIP5K with auxin-related processes has not yet been directly investigated. Here we report on the functional characterization of Arabidopsis PIP5K2, which is expressed in various tissues and whose expression is enhanced by exogenous auxin.…”