SUMMARY Physalis grisea is a widely valued orphan crop with medicinal properties and edible functional fruits. Under global warming, high temperature stress (HTS) severely restricts the growth and development of P. grisea , while the epigenetic regulatory mechanism underlying its HTS response remains largely unclear. In this study, we identified the ZINC FINGER HOMEODOMAIN (ZHD) transcription factor PgZHD18 as a positive regulator of basal thermotolerance in P. grisea . Functional assays showed that PgZHD18 enhances basal thermotolerance by improving ROS scavenging capacity, alleviating membrane damage, and maintaining chlorophyll stability. Further molecular verification revealed that PgZHD18 directly binds to the promoters of key lignin biosynthetic genes ( PgPAL1 , PgC3H1 , PgC4H , PgCAD3 ) and activates their transcription, thus promoting lignin accumulation. Moreover, PgZHD18 interacts with the Trithorax Group (TrxG) protein PgWDR5b, which increases H3K4me3 deposition at the promoters of lignin biosynthetic genes and further amplifies their transcriptional activation, synergistically enhancing basal thermotolerance. Collectively, our findings reveal a dual regulatory module of transcriptional activation coupled with epigenetic modification in plant heat response, and provide a theoretical basis and molecular targets for breeding heat‐resistant crop varieties.
SUMMARY The southern African endemic tree Greyia Hook. & Harv. (Francoaceae, Geraniales) comprises three species distinguished by striking variation in trichome morphology and inflorescence architecture, yet the genomic and regulatory basis of these traits has remained largely unexplored. Here, we present chromosome‐scale genome assemblies for all recognised Greyia species, namely Greyia radlkoferi , Greyia sutherlandii , and Greyia flanaganii , providing the first high‐quality genomic resources for Geraniales. Phylogenomic analyses placed Geraniales as sister to Crossosomatales, with divergence at ~103 million years ago (Mya), and indicated that Greyia diversified recently during the Quaternary (~1.39 Mya). Comparative genomics revealed a Greyia ‐specific palaeo‐hexaploidisation event dated to ~87 Mya, followed by fractionation but with extensive retention of ancestral gene sets in either triplicated or duplicated states across syntenic regions. Transcriptomic analyses revealed regulatory divergence in the conserved MYB–bHLH–WD40 (MBW) network likely associated with variation in trichome morphology, including undetectable GL1 expression and altered GL3/EGL3 expression in G. sutherlandii . In addition, analyses of flower and inflorescence traits identified expansion of MADS‐box transcription factor families and species‐specific cis ‐regulatory divergence in LFY and FT . Notably, predicted AGL6 binding sites are retained in the LFY and FT promoters of G. radlkoferi and G. sutherlandii but absent in G. flanaganii , consistent with differences in inflorescence density among species. Together, these results demonstrate how polyploidy and regulatory divergence of conserved developmental pathways have shaped morphological diversification in Greyia .
SUMMARY Soybean ( Glycine max (L.) Merr.) produces triterpenoid saponins, called soyasaponins, which are categorised as 2,3‐dihydro‐2,5‐dihydroxy‐6‐methyl‐4 H ‐pyran‐4‐one (DDMP) saponins and group A saponins based on the chemical modifications at the C‐22 position of their triterpene skeleton. These C‐22 modifications confer different biological functions. While most genes involved in soyasaponin biosynthesis have been identified, the enzymes responsible for conjugation of DDMP or arabinose to the C‐22 hydroxyl group remain unclear. This study aimed to identify the enzymes involved in these modifications. Co‐expression analysis using known saponin biosynthetic genes identified three candidate UGT genes. Among them, UGT73K5 was essential for DDMP saponin biosynthesis in soybean, as ugt73k5 mutants lacked these compounds. Similarly, the orthologous gene in Lotus japonicus , UGT73K6 , was required for DDMP saponin biosynthesis, and the ugt73k6 defect was complemented by soybean UGT73K5 . In addition, UGT73BU1 , a homologous gene not co‐expressed with known saponin biosynthetic genes, was identified as a C‐22 arabinosyltransferase involved in group A saponin biosynthesis. In L. japonicus , UGT73K6 is genomically co‐localised and co‐expressed with a cytochrome P450 gene responsible for C‐22 hydroxylation, forming a conserved biosynthetic gene cluster. This organisation suggests coordinated biosynthetic modules underlying DDMP saponin production in legumes.
