Extracellular signal peptide that regulates cell fate (PubMed:16902140). Represses root apical meristem maintenance (PubMed:16902140, PubMed:23569225). Represses protophloem differentiation in a BAM3-dependent manner (PubMed:23569225). BRX, BAM3, and CLE45 act together to regulate the transition of protophloem cells from proliferation to differentiation, thus impinging on postembryonic growth capacity of the root meristem; this signaling pathway requires CRN and CLV2 and involves MAKR5 for its transduction/amplification (PubMed:23569225, PubMed:27354416, PubMed:28607033). Triggers the accumulation of MAKR5 in developing sieve elements in a BAM3-dependent manner (PubMed:27354416). Prevents, in a dose-dependent manner, auxin response in the root meristem thus leading in the repression of protophloem differentiation and periclinal sieve element precursor cell division (PubMed:25049386). Promotes pollen tube growth prolongation in a SKM1 and SKM2-dependent manner, especially under relatively high temperature (at 30 degrees Celsius), thus conferring tolerance against high temperature probably through the maintenance of mitochondrial activity (PubMed:23910659). Alleviates mitochondrial decay pollen tube in vitro culture (PubMed:23910659). Binds to SKM1 present in the pollen grain, particularly under relatively high temperature (at 30 degrees Celsius) (PubMed:23910659). Interacts with BAM3, especially in roots (PubMed:28607033). Expressed at low levels in flowers, especially in pistils (PubMed:16489133, PubMed:23910659). Present in vascular tissues (PubMed:23910659). In roots, confined to protophloem and sieve element precursor cells (PubMed:25049386, PubMed:23569225). In flowers, at 22 degrees Celsius, preferentially expressed in the stigma in the pistil, but expands to the transmitting tract, along which pollen tubes elongated, upon temperature shift to 30 degrees Celsius (PubMed:23910659). Expressed in roots developing protophloem, up to the end of the transition zone (PubMed:23569225). A shift from 22 degrees Celsius to 30 degrees Celsius leads to a modified spatial repartition in flowers. Reduced seed production at 30 degrees Celsius, but not at 22 degrees Celsius. Belongs to the CLV3/ESR signal peptide family. Extended C-terminus.