Plants have mechanisms to recognize and reject pollen from other species. Although widespread, these mechanisms are less well understood than the self‐incompatibility (
Plants make a variety of specialized metabolites that can mediate interactions with animals, microbes, and competitor plants. Understanding how plants synthesize these compounds enables studies of their biological roles by manipulating their synthesis in vivo as well as producing them in vitro. Acylsugars are a group of protective metabolites that accumulate in the trichomes of many Solanaceae family plants. Acylinositol biosynthesis is of interest because it appears to be restricted to a subgroup of species within the Solanum genus. Previous work characterized a triacylinositol acetyltransferase involved in acylinositol biosynthesis in the Andean fruit plant
- NSF-PAR ID:
- 10445194
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Plant Direct
- Volume:
- 6
- Issue:
- 6
- ISSN:
- 2475-4455
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
more » « less
Summary SI ) mechanisms plants use to reject pollen from close relatives. Previous studies have shown that some interspecific reproductive barriers (IRB s) are related toSI in the Solanaceae. For example, the pistilSI proteins S‐RN ase andHT protein function in a pistil‐sideIRB that causes rejection of pollen from self‐compatible (SC ) red/orange‐fruited species in the tomato clade. However, S‐RN ase‐independentIRB s also clearly contribute to rejecting pollen from these species. We investigated S‐RN ase‐independent rejection ofSolanum lycopersicum pollen bySC Solanum pennellii LA 0716,SC .Solanum habrochaites LA 0407, andSC Solanum arcanum LA 2157, which lack functional S‐RN ase expression. We found that all three accessions expressHT proteins, which previously had been known to function only in conjunction with S‐RN ase, and then usedRNA i to test whether they also function in S‐RN ase‐independent pollen rejection. SuppressingHT SC S. pennellii LA 0716 allowsS. lycopersicum pollen tubes to penetrate farther into the pistil inHT HT SC .Solanum habrochaites LA 0407 and inSC S. arcanum LA 2157 allowsS. lycopersicum pollen tubes to penetrate to the ovary and produce hybrids that, otherwise, would be difficult to obtain. Thus,HT proteins are implicated in both S‐RN ase‐dependent and S‐RN ase‐independent pollen rejection. The results support the view that overall compatibility results from multiple pollen–pistil interactions with additive effects. -
more » « less
Summary Many
Actinidia cultivars are characterized by anthocyanin accumulation, specifically in the inner pericarp, but the underlying regulatory mechanism remains elusive. Here we report two interacting transcription factors, AcMYB 123 and AcbHLH 42, that regulate tissue‐specific anthocyanin biosynthesis in the inner pericarp ofActinidia chinensis cv. Hongyang. Through transcriptome profiling analysis we identified fiveMYB and threebHLH transcription factors that were upregulated in the inner pericarp. We show that the combinatorial action of two of them, AcMYB 123 and AcbHLH 42, is required for activating promoters ofAcANS andAcF3GT1 that encode the dedicated enzymes for anthocyanin biosynthesis. The presence of anthocyanin in the inner pericarp appears to be tightly associated with elevated expression ofAcMYB123 andAcbHLH42 .RNA interference repression ofAcMYB123 ,AcbHLH42 ,AcF3GT1 andAcANS in ‘Hongyang’ fruits resulted in significantly reduced anthocyanin biosynthesis. Using both transient assays inNicotiana tabacum leaves orActinidia arguta fruits and stable transformation in Arabidopsis, we demonstrate that co‐expression ofAcMYB123 andAcbHLH42 is a prerequisite for anthocyanin production by activating transcription ofAcF3GT1 andAcANS or the homologous genes. Phylogenetic analysis suggests that AcMYB 123 or AcbHLH 42 are closely related toTT 2 orTT 8, respectively, which determines proanthocyanidin biosynthesis in Arabidopsis, and to anthocyanin regulators in monocots rather than regulators in dicots. All these experimental results suggest that AcMYB 123 and AcbHLH 42 are the components involved in spatiotemporal regulation of anthocyanin biosynthesis specifically in the inner pericarp of kiwifruit. -
more » « less
Summary Plant small
RNA s (sRNA s) modulate key physiological mechanisms through post‐transcriptional and transcriptional silencing of gene expression. SmallRNA s fall into two major categories: those are reliant onRNA ‐dependentRNA polymerases (RDR RDR 12 /6 ‐dependentsRNA s include phased and repeat‐associated short interferingRNA s, while knownRDR 12 /6 ‐independentsRNA s are primarily microRNA s (miRNA ) and other hairpin‐derivedsRNA s. In this study we produced and analyzedsRNA ‐seq libraries fromrdr1 /rdr2 /rdr6 triple mutant plants. We found 58 previously annotated miRNA loci that were reliant onRDR 12 , or ‐6 function, casting doubt on their classification. We also found 38RDR 12 /6‐independentsRNA loci that are notMIRNA sRNA biogenesis. These 38sRNA ‐producing loci have as‐yet‐undescribed biogenesis mechanisms, and are frequently located in the vicinity of protein‐coding genes. Altogether, our analysis suggests that these 38 loci represent one or more undescribed types ofsRNA inArabidopsis thaliana . -
more » « less
Summary Euonymus alatus diacylglycerol acetyltransferase (Ea DA cT) catalyzes the transfer of an acetyl group from acetyl‐CoA to thesn ‐3 position of diacylglycerol to form 3‐acetyl‐1,2‐diacyl‐sn ‐glycerol (acetyl‐TAG ).Ea DA cT belongs to a small, plant‐specific subfamily of the membrane bound O‐acyltransferases (MBOAT ) that acylate different lipid substrates. Sucrose gradient density centrifugation revealed thatEa DA cT colocalizes to the same fractions as an endoplasmic reticulum (ER )‐specific marker. By mapping the membrane topology ofEa DA cT, we obtained an experimentally determined topology model for a plantMBOAT . TheEa DA cT model contains four transmembrane domains (TMD s), with both the N‐ and C‐termini orientated toward the lumen of theER . In addition, there is a large cytoplasmic loop between the first and secondTMD s, with theMBOAT signature region of the protein embedded in the thirdTMD close to the interface between the membrane and the cytoplasm. During topology mapping, we discovered two cysteine residues (C187 and C293) located on opposite sides of the membrane that are important for enzyme activity. In order to identify additional amino acid residues important for acetyltransferase activity, we isolated and characterized acetyltransferases from other acetyl‐TAG ‐producing plants. Among them, the acetyltransferase fromEuonymus fortunei possessed the highest activityin vivo andin vitro . Mutagenesis of conserved amino acids revealed that S253, H257, D258 and V263 are essential forEa DA cT activity. Alteration of residues unique to the acetyltransferases did not alter the unique acyl donor specificity ofEa DA cT, suggesting that multiple amino acids are important for substrate recognition. -
more » « less
Summary In plants, 24 nucleotide long heterochromatic si
RNA s (het‐siRNA s) transcriptionally regulate gene expression byRNA ‐directedDNA methylation (RdDM ). The biogenesis of most het‐siRNA s depends on the plant‐specificRNA polymeraseIV (PolIV ), andARGONAUTE 4 (AGO 4) is a major het‐siRNA effector protein. Through genome‐wide analysis ofsRNA ‐seq data sets, we found thatAGO 4RNA s. The accumulation ofAGO 4RNA s also requires several factors known to participate in the effector portion of the RdDM pathway, includingRNA POLYMERASE V (POL V),DOMAINS REARRANGED METHYLTRANSFERASE 2 (DRM 2) andSAWADEE HOMEODOMAIN HOMOLOGUE 1 (SHH 1). Like manyAGO proteins,AGO 4 is an endonuclease that can ‘slice’RNA s. We found that a slicing‐defectiveAGO 4 was unable to fully recoverAGO 4‐RNA accumulation fromago4 mutant plants. Collectively, our data suggest thatAGO 4RNA s are secondary siRNA s dependent on the prior activity of the RdDM pathway at certain loci.
