TDIF Peptide Signaling Regulates Vascular Stem Cell Proliferation via theWOX4Homeobox Gene inArabidopsis 

Abstract

The indeterminate nature of plant growth and development depends on the stem cell system found in meristems. The Arabidopsis thaliana vascular meristem includes procambium and cambium. In these tissues, cell-cell signaling, mediated by a ligand-receptor pair made of the TDIF (for tracheary element differentiation inhibitory factor) peptide and the TDR/PXY (for TDIF RECEPTOR/ PHLOEM INTERCALATED WITH XYLEM) membrane protein kinase, promotes proliferation of procambial cells and suppresses their xylem differentiation. Here, we report that a WUSCHEL-related HOMEOBOX gene, WOX4, is a key target of the TDIF signaling pathway. WOX4 is expressed preferentially in the procambium and cambium, and its expression level was upregulated upon application of TDIF in a TDR-dependent manner. Genetic analyses showed that WOX4 is required for promoting the proliferation of procambial/cambial stem cells but not for repressing their commitment to xylem differentiation in response to the TDIF signal. Thus, at least two intracellular signaling pathways that diverge after TDIF recognition by TDR might regulate independently the behavior of vascular stem cells. Detailed observations in loss-of-function mutants revealed that TDIF-TDR-WOX4 signaling plays a crucial role in the maintenance of the vascular meristem organization during secondary growth.

A comparative transcriptomic approach to understanding the formation of cork

“…These results are consistent with FLC downregulation in cork oak phellem as this MADS-box transcription factor is a floral repressor found upstream of AP1 in the signal transduction pathway (Andrés and Coupland 2012). ARK1/STM and WOX4 have been related to stem cell maintenance in cambium (Groover et al 2006;Hirakawa et al 2010). ARK1/STM prevents the differentiation of meristematic cells (Groover et al 2006), whereas WOX4 has been shown to trigger auxin responsiveness in the cambial meristem to promote cambial proliferation (Ji et al 2010;Suer et al 2011).…”

Plant GSK3 proteins regulate xylem cell differentiation downstream of TDIF–TDR signalling

“…To investigate roles of SKI and II members in TDIF signalling, TDIF sensitivity was examined by genetic analysis using loss-of-function mutants for GSK3s. Previous physiological and genetic studies have shown that TDIF has two distinct effects on vascular development; inhibition of xylem differentiation and promotion of vascular cell division 15,16,18 . In the WT, exogenous TDIF application suppresses xylem differentiation from procambial cells, resulting in discontinuous xylem formation in Arabidopsis leaf veins 16,18 ( Fig.…”

“…TDIF both suppresses the differentiation of procambial cells into xylem cells and promotes their proliferation through TDR 15,16 . These dual functions of TDIF-TDR are considered to be separated by downstream components 18 . A transcription factor WUSCHEL-related HOMEOBOX 4 (WOX4) is a target of the TDIF-TDR signalling pathway leading to cell proliferation but not to xylem differentiation 18 .…”

“…These dual functions of TDIF-TDR are considered to be separated by downstream components 18 . A transcription factor WUSCHEL-related HOMEOBOX 4 (WOX4) is a target of the TDIF-TDR signalling pathway leading to cell proliferation but not to xylem differentiation 18 . However, until now, the intracellular signalling components leading to the inhibition of xylem differentiation remain elusive.…”

A wound-induced small polypeptide gene family is upregulated in soybean nodules

“…Many small peptides have been identified recently in different plants, such as defensin [1], systemin [2], PSK (phytosulfokine) [3], ENOD40 [4], CLV3 [5], POLARIS [6], IDA [7], DVL1 [8], PSY1 [9], TDIF [10], RGF [11], CLE2 [5], CEP1 [12], RALF [13], Stomagen [14], EPF1 [15], FPF1 [16], SCR [17], LURE [18], TPD1 [19] and NCR [20]. Some of these peptides including PSK, CLV3, RGF, EPF1, FPF1, POLARIS, ENOD40 and RALF are involved in cell differentiation and organ development, and thus are designated as peptide hormones.…”