Regeneration of a tissue damaged by injury represents a physiological response for organ recovery. Although this regeneration process is conserved across multicellular taxa, plants appear to display extremely high regenerative capacities, a feature widely used in tissue culture for clonal propagation and grafting. Regenerated cells arise predominantly from pre-existing populations of division-competent cells; however, the mechanisms by which these cells are triggered to divide in response to injury remain largely elusive. Here, we demonstrate that the heterodimeric transcription factor complex ETHYLENE RESPONSE FACTOR115 (ERF115)-PHYTOCHROME A SIGNAL TRANSDUCTION1 (PAT1) sustains meristem function by promoting cell renewal after stem cell loss. High-resolution time-lapse imaging revealed that cell death promotes ERF115 activity in cells that are in direct contact with damaged cells, triggering divisions that replenish the collapsed stem cells. Correspondingly, the ERF115-PAT1 complex plays an important role in full stem cell niche recovery upon root tip excision, whereas its ectopic expression triggers neoplastic growth, correlated with activation of the putative target gene WOUND INDUCED DEDIFFERENTIATION1 (WIND1). We conclude that the ERF115-PAT1 complex accounts for the high regenerative potential of plants, granting them the ability to efficiently replace damaged cells with new ones.

Plants are known for their outstanding capacity to recover from various wounds and injuries. However, it remains largely unknown how plants sense diverse forms of injury and canalize existing developmental processes into the execution of a correct regenerative response. Auxin, a cardinal plant hormone with morphogen-like properties, has been previously implicated in the recovery from diverse types of wounding and organ loss. Here, through a combination of cellular imaging and in silico modeling, we demonstrate that vascular stem cell death obstructs the polar auxin flux, much alike rocks in a stream, and causes it to accumulate in the endodermis. This in turn grants the endodermal cells the capacity to undergo periclinal cell division to repopulate the vascular stem cell pool. Replenishment of the vasculature by the endodermis depends on the transcription factor ERF115, a wound-inducible regulator of stem cell division. Although not the primary inducer, auxin is required to maintain ERF115 expression. Conversely, ERF115 sensitizes cells to auxin by activating ARF5/MONOPTEROS, an auxin-responsive transcription factor involved in the global auxin response, tissue patterning, and organ formation. Together, the wound-induced auxin accumulation and ERF115 expression grant the endodermal cells stem cell activity. Our work provides a mechanistic model for wound-induced stem cell regeneration in which ERF115 acts as a wound-inducible stem cell organizer that interprets wound-induced auxin maxima.

Salinity is one of the important abiotic stress factors that limit crop production. Common bean, Phaseolus vulgaris L., a major protein source in developing countries, is highly affected by soil salinity and the information on genes that play a role in salt tolerance is scarce. We aimed to identify differentially expressed genes (DEGs) and related pathways by comprehensive analysis of transcriptomes of both root and leaf tissues of the tolerant genotype grown under saline and control conditions in hydroponic system. We have generated a total of 158 million high-quality reads which were assembled into 83,774 all-unigenes with a mean length of 813 bp and N50 of 1,449 bp. Among the all-unigenes, 58,171 were assigned with Nr annotations after homology analyses. It was revealed that 6,422 and 4,555 all-unigenes were differentially expressed upon salt stress in leaf and root tissues respectively. Validation of the RNA-seq quantifications (RPKM values) was performed by qRT-PCR (Quantitative Reverse Transcription PCR) analyses. Enrichment analyses of DEGs based on GO and KEGG databases have shown that both leaf and root tissues regulate energy metabolism, transmembrane transport activity, and secondary metabolites to cope with salinity. A total of 2,678 putative common bean transcription factors were identified and classified under 59 transcription factor families; among them 441 were salt responsive. The data generated in this study will help in understanding the fundamentals of salt tolerance in common bean and will provide resources for functional genomic studies.

Plants react to wounding through the activation of both defense and repair pathways, but how these two responses are coordinated is unclear. Here, we put forward the hypothesis that diverse members of the subfamily X of the plant-specific ethylene response factor (ERF) transcription factors coordinate stress signaling with the activation of wound repair mechanisms. Moreover, we highlight the observation that tissue repair is strongly boosted through the formation of a heterodimeric protein complex that comprises ERF and transcription factors of the GRAS domain type. This interaction turns ERFs into highly potent and stress-responsive activators of cell proliferation. The potency to induce stem cell identity suggests that these heterodimeric transcription factor complexes could become valuable tools to increase crop regeneration and transformation efficiency.