The ScRALF3 secreted peptide is involved in sporophyte to gametophyte signalling and affects pollen mitosis I

Abstract

Signalling events through small peptides are essential in multiple aspects of plant reproduction. The ScRALF3 Solanum chacoense Rapid Alkalinization Factor (RALF) peptide was previously shown to regulate multiple aspects of cell–cell communication between the surrounding sporophytic tissue and the female gametophyte during ovule development. We analysed the global expression pattern of ScRALF3 with GUS reporter gene under control of the ScRALF3 promoter and validated it with in situ hybridisation. To better understand the role of ScRALF3 we used three different RNA interference (RNAi) lines that reduced the expression of ScRALF3 during pollen development. Both expression methods showed the presence of ScRALF3 in different tissues, including stigma, style, vascular tissues and during stamen development. Down‐regulation of ScRALF3 expression through RNAi showed drastic defects in early stages of pollen development, mainly on the first mitosis. These results suggest that the ScRALF3 secreted peptide regulates the transition from sporogenesis to gametogenesis in both male and female gametophytes.

The Genome-Wide Analysis of RALF-Like Genes in Strawberry (Wild and Cultivated) and Five Other Plant Species (Rosaceae)

“…The GO terms give a clear function cluster of RALF-like genes, which involved in the pollen tube development, root development, negative regulation of growth, cell wall growth, hormone activaty, brassinosteroid-mediated signaling pathway, and so on. According to the classification, we found they are very consistent with previous researches about the functions of RALF genes [1,[14][15][16][17][18]64]. Fungal infection response and pollen tube development are important for Rosaceae species, and the RALF-like gene expression in seed and fruit among Rosaceae species specially.…”

“…As reported, RALF genes are not only involved in several biotic and abiotic stresses but also influence the growth and development of plants. Here, we found that the expression profiles are mostly similar with the researchers reported, such as the drought response [13], root growth [64], hormone response [18], fungi response [18][19][20], cell wall development [15,17], and the flower development (especially the development of pollen tube) [14,16]. In the present study, we combined the results of RNA-seq, EST data, cis-regulatory elements analysis, and RT-qPCR to identify several genes which have identical expression profiles in two or more analyses, which may give some instructions of the research of RALF-like genes among Rosaceae species.…”

“…RNA-seq consistent with cis-regulatory element analysis involved in Fv-RALF1, Fv-RALF2, Fv-RALF12, Fv-RALF15 (seed, embyro, and endosperm), which have no research reported, may be the special findings in our study among Rosaceae species. The RALF genes most reported were the role they play in root growth and pollen tube development [14,16]. Here, the comparison between RNA-seq and EST data reveal that Md-RALF3 may have influence on the growth of young root, and Md-RALF7 and Md-RALF8 may affect the development of flowers.…”

“…Moussu et al [15] reported the crystal structure of the LRX-RALF cell wall complex and demonstrated that RALF peptides were activated as folded proteins, and RALFs can also instruct LRX cell wall modules and CrRKL1L receptors through structurally different binding modes to coordinate pollen tube integrity. ScRALF23 was reported as able to affect the pollen mitosis by functioning among the process from sporophyte to gametophyte signaling [16]. Leucine-rich repeat extension proteins can combine with RALF to modify cell wall expansion and bind to the transmembrane receptor FERONIA and regulate the cell growth [17].…”

RALF peptides modulate immune response in the mossPhyscomitrium patens

“…RALF peptides are involved in the regulation of root growth, pollen tube elongation, formation of nitrogen-fixing nodules and inulin accumulation (Murphy and De Smet, 2014; Tena, 2016; Wieghaus et al, 2019). Also, they are involved in the processes of intercellular communication between sporophyte and gametophyte in land plants (Chevalier et al, 2013; Mecchia et al, 2017; Loubert-Hudon et al, 2020). The function of RALF genes that have been identified in bryophyte genomes are still being studied.…”