枯草杆菌蛋白酶介导的EPF1/EPF2成熟加工对气孔模式形成至关重要

Abstract

Proper stomatal distribution optimizes the balance between acquiring atmospheric CO 2 for photosynthesis and minimizing water loss 1 , 2 . In Arabidopsis , the EPIDERMAL PATTERNING FACTOR (EPF)–ERECTA family signalling pathway specifies this patterning 2 , 3 , 4 , 5 , 6 . Similar to most signalling peptides, EPF1 and EPF2 require proteolytic processing to convert inactive precursor proteins into functional mature peptides 7 ; however, in contrast to the well-characterized signalling cascade downstream of the ERECTA family 2 , little is known about the mechanisms of proteolytic release of the mature EPF1/2 from precursors. Here we identify a group of subtilisin-like serine proteinases 8 , designated as EPF-PROCESSING PROTEINASES (EPPs), which play a crucial role in stomatal patterning by processing EPF1 and EPF2 precursors. Loss-of-function mutations in EPPs lead to a dramatic increase and clustering of stomata, resembling the phenotypes observed in epf1/2 and er-105 erl1/2 mutants. Notably, these defects can be mitigated through the exogenous application of mature EPF1/2 peptides. Moreover, mutations of these EPPs inhibit the cleavage of EPF1/2 precursors and attenuate their associated overexpression phenotypes. Furthermore, biochemical assays demonstrate that EPPs cleave EPF1/2 both in vitro and in vivo. Taken together, our findings elucidate the molecular mechanisms underlying EPP-mediated processing of EPF1/2 precursors. This proteolytic release of active peptides is identified as a critical, previously missing link required for establishing proper stomatal patterning in plants.