Secreted Peptide Signals Required for Maintenance of Root Stem Cell Niche in Arabidopsis

Abstract

Stem cells are maintained in the niche by intercellular interactions and signaling networks. In this work, we study extracellular signals required for maintenance of the root stem cell niche in higher plants. We identify a family of functionally redundant homologous peptides that are secreted, tyrosine-sulfated, and expressed mainly in the stem cell area and the innermost layer of central columella cells. We name these peptides root meristem growth factors (RGFs). RGFs are required for maintenance of the root stem cell niche and transit amplifying cell proliferation in Arabidopsis. RGF1 defines expression levels and patterns of the stem cell transcription factor PLETHORA, mainly at the posttranscriptional level. The RGFs function independently of the auxin pathway. These peptide signals play a crucial role in postembryonic root development.

MYB30 regulates root cell elongation under abscisic acid signaling

“…In addition to auxin and cytokinin, Jasmonate is known as a regulator of PLT expression through MYC2 [7]. Root growth factor (RGF), which is a peptide hormone, also regulates PLT activity [8]. These findings indicate that regulation of cell proliferation by PLT is one of the major events in the root meristematic zone for controlling root growth.…”

RGF1 INSENSITIVE 1 to 5, a group of LRR receptor-like kinases, are essential for the perception of root meristem growth factor 1 in Arabidopsis thaliana

“…These peptides are expressed in the root meristem region and are responsible for root meristem maintenance. This family of peptides was initially designated as ROOT MERI-STEM GROWTH FACTORS (RGFs) [25]. The same family of peptides was also named CLEL because of the CLEL motifs at their C-termini [26], or GOLVEN (GLV) as transgenic plants overexpressing RGF precursor genes showed wavy root phenotypes on slanted plates, suggesting their roles in regulating plant gravitropic responses [27].…”

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

“…Twenty-eight of 38 families are conserved in A .thaliana, but 5 only exist in soybean, and the other five also exist in M. truncatula and Lotus japonicas ( Table 2). The other six conserved gene families, such as PSK [3], RGF (root meristem growth factor) [11], EPF1 (epithermal patterning factor 1) [15], FPF1 (flowering promoting factor 1) [16], AGP (arabinosylated glycopeptide) [28] and DVL (DEVIL 1) [8], have been studied previously. …”

“…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.…”