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• Heteromorphic diaspores (fruits and seeds) are an adaptive bet-hedging strategy to cope with spatiotemporally variable environments, particularly fluctuations in favourable temperatures and unpredictable precipitation regimes in arid climates. • We conducted comparative analyses of the biophysical and ecophysiological properties of the two distinct diaspores (mucilaginous seed (M⁺) vs indehiscent (IND) fruit) in the dimorphic annual Aethionema arabicum (Brassicaceae), linking fruit biomechanics, dispersal aerodynamics, pericarp-imposed dormancy, diaspore abscisic acid (ABA) concentration, and phenotypic plasticity of dimorphic diaspore production to its natural habitat and climate. • Two very contrasting dispersal mechanisms of the A. arabicum dimorphic diaspores were revealed. Dehiscence of large fruits leads to the release of M⁺ seed diaspores, which adhere to substrata via seed coat mucilage, thereby preventing dispersal (antitelechory). IND fruit diaspores (containing nonmucilaginous seeds) disperse by wind or water currents, promoting dispersal (telechory) over a longer range. • The pericarp properties confer enhanced dispersal ability and degree of dormancy on the IND fruit morph to support telechory, while the M⁺ seed morph supports antitelechory. Combined with the phenotypic plasticity to produce more IND fruit diaspores in colder temperatures, this constitutes a bet-hedging survival strategy to magnify the prevalence in response to selection pressures acting over hilly terrain.

Two genes controlling the purple pericarp trait in wheat, TaPpm1 and TaPpb1, are identified and the mechanism by which they co-regulate anthocyanin synthesis is proposed. Abstract Purple pericarps of bread wheat (Triticum aestivum L.) are a useful source of dietary anthocyanins. Previous mapping results indicated that the purple pericarp trait is controlled by two complementary genes located on chromosomes 7D and 2A. However, the identity of the genes and the mechanisms by which they regulate the trait are unknown. In this study, two transcription factors were characterised as anthocyanin activators in purple pericarps: TaPpm1 (purple pericarp-MYB 1) and TaPpb1 (purple pericarp-bHLH 1). Three non-functional variants were detected in the coding sequence of TaPpm1 from non-purple seed lines, in which the function of TaPpm1 was destroyed either by insertion-induced frame shifts or truncated peptides. There were six 261-bp tandem repeats in the promoter region of TaPpb1 in the purple-grained varieties, while there was only one repeat unit present in the non-purple varieties. Furthermore, using yeast two-hybrid, dual luciferase, yeast one-hybrid, and transient assays, we were able to demonstrate that the interaction of TaPpm1 and TaPpb1 co-regulates the synthesis of anthocyanin. Overall, our results provide a better understanding of the molecular basis of anthocyanin synthesis in the wheat pericarp and indicate the existence of an integrated regulatory mechanism that controls production.

Despite the relevance of seed-filling mechanisms for crop yield, we still have only a rudimentary understanding of the transport processes that supply the caryopsis with sugars. We hypothesized that SWEET sucrose transporters may play important roles in nutrient import pathways in the rice caryopsis. We used a combination of mRNA quantification, histochemical analyses, translational promoter–reporter fusions and analysis of knockout mutants created by genomic editing to evaluate the contribution of SWEET transporters to seed filling. In rice caryopses, SWEET11 and 15 had the highest mRNA levels and proteins localized to four key sites: all regions of the nucellus at early stages; the nucellar projection close to the dorsal vein; the nucellar epidermis that surrounds the endosperm; and the aleurone. ossweet11;15 double knockout lines accumulated starch in the pericarp, whereas caryopses did not contain a functional endosperm. Jointly, SWEET11 and 15 show all the hallmarks of being necessary for seed filling with sucrose efflux functions at the nucellar projection and a role in transfer across the nucellar epidermis/aleurone interface, delineating two major steps for apoplasmic seed filling, observations that are discussed in relation to observations made in rice and barley regarding the relative prevalence of these two potential import routes.

Summary The repeated emergence of the same trait (convergent evolution) in distinct species is an interesting phenomenon and manifests visibly the power of natural selection. The underlying genetic mechanisms have important implications to understand how the genome evolves under environmental challenges. In cereal crops, both rice and barley can develop black‐coloured husk/pericarp due to melanin accumulation. However, it is unclear if this trait shares a common origin. Here, we fine‐mapped the barley HvBlp gene controlling the black husk/pericarp trait and confirmed its function by gene silencing. The result was further supported by a yellow husk/pericarp mutant with deletion of the HvBlp gene, derived from gamma ray radiation of the wild‐type W1. HvBlp encodes a putative tyrosine transporter homologous to the black husk gene OsBh4 in rice. Surprisingly, synteny and phylogenetic analyses showed that HvBlp and OsBh4 belonged to different lineages resulted from dispersed and tandem duplications, respectively, suggesting that the black husk/pericarp trait has emerged independently. The dispersed duplication (dated at 21.23 MYA) yielding HvBlp occurred exclusively in the common ancestor of Triticeae. HvBlp and OsBh4 displayed converged transcription in husk/pericarp tissues, contributing to the black husk/pericarp trait. Further transcriptome and metabolome data identified critical candidate genes and metabolites related to melanin production in barley. Taken together, our study described a compelling case of convergent evolution resulted from transcriptional convergence after repeated gene duplication, providing valuable genetic insights into phenotypic evolution. The identification of the black husk/pericarp genes in barley also has great potential in breeding for stress‐resilient varieties with higher nutritional values.

A high purity polysaccharide (UELPP-A1) was isolated from the crude polysaccharide of litchi pericarp (UELPP) by column chromatography, and acetylated polysaccharide (AC-UELPP) was obtained by acetylation modification of the crude polysaccharide of litchi pericarp. The physicochemical properties and in vitro antioxidant activity of UELPP-A1 and AC-UELPP were compared. The C/H on UELPP-A1 was assigned by Congo red test, FTIR, 1D and 2D NMR, and its structural characteristics were characterized. The results showed that the total sugar content of neutral UELPP-A1 was significantly increased to 94.15%, and its structure did not have a triple helix structure. In addition, the in vitro antioxidant activity test showed that both polysaccharides had antioxidant activity in a dose-dependent manner. The enhancement effect of AC-UELPP with the increase of concentration was the most significant ( P  < 0.05). Among them, the hydroxyl radical scavenging activity was stronger than its reducing ability and superoxide anion radical at the same polysaccharide concentration. Acetylation modification can improve the antioxidant activity of UELPP and has further research value for human health care.

Long-term storage of pear fruit at low temperature can retard senescence but may result in pericarp browning. We previously reported that increasing endogenous γ-aminobutyrate (GABA) content by exogenous GABA treatment can maintain mitochondrial structure integrity, thereby alleviating pericarp browning of ‘Nanguo’ pears after cold storage. Here, we tested the effectiveness of Ca2+ treatment on pericarp browning in relation to GABA biosynthesis. Fruit browning was reduced by treatment with Ca2+ after 180 days of storage. Pericarp Ca2+ and calmodulin content in treated fruit increased, and concomitantly, endogenous GABA content, key GABA synthesis-related enzyme activity, and gene expression were upregulated. Moreover, the mitochondrial structure in the pericarp tissue was found to be well preserved. Thus, Ca2+ treatment effectively reduced pericarp browning of refrigerated ‘Nanguo’ pears owing to improvement in the GABA biosynthesis capacity in the fruit.

Background Akebia trifoliata (Thunb.) Koidz may have applications as a new potential source of biofuels owing to its high seed count, seed oil content, and in-field yields. However, the pericarp of A. trifoliata cracks longitudinally during fruit ripening, which increases the incidence of pests and diseases and can lead to fruit decay and deterioration, resulting in significant losses in yield. Few studies have evaluated the mechanisms underlying A. trifoliata fruit cracking. Results In this study, by observing the cell wall structure of the pericarp, we found that the cell wall became thinner and looser and showed substantial breakdown in the pericarp of cracking fruit compared with that in non-cracking fruit. Moreover, integrative analyses of transcriptome and proteome profiles at different stages of fruit ripening demonstrated changes in the expression of various genes and proteins after cracking. Furthermore, the mRNA levels of 20 differentially expressed genes were analyzed, and parallel reaction monitoring analysis of 20 differentially expressed proteins involved in cell wall metabolism was conducted. Among the molecular targets, pectate lyases and pectinesterase, which are involved in pentose and glucuronate interconversion, and β-galactosidase 2, which is involved in galactose metabolism, were significantly upregulated in cracking fruits than in non-cracking fruits. This suggested that they might play crucial roles in A. trifoliata fruit cracking. Conclusions Our findings provided new insights into potential genes influencing the fruit cracking trait in A. trifoliata and established a basis for further research on the breeding of cracking-resistant varieties to increase seed yields for biorefineries.

Pericarp coloration is an important trait in Akebia trifoliata breeding which influences consumer choice. To better understand the molecular mechanisms underlying its formation, three varieties of A. trifoliata with different pericarp colors: Luoyang white pericarp (LW), Guida No.3 pink pericarp (GP), and Za No.30 purple pericarp (ZP) were used. The pigment content of the pericarp of these three varieties during the colour change period was determined, and anthocyanins were determined as the main reason for the different colors. RNA-Seq analysis was performed on the pericarps of different varieties over several periods. Using LW as a control, 13,807 differently expressed genes (DEGs) were identified by comparing the GP and ZP. KEGG enrichment analysis revealed that phenylalanine and flavonoid biosynthesis were significantly enriched, and anthocyanin regulatory genes such as AtrPAL , AtrCHS , AtrCHI and AtrANS were identified. Weighted gene coexpression network analysis (WGCNA) identified two modules highly related to anthocyanin biosynthesis and showed that AtrANS plays a vital role in anthocyanin biosynthesis in the pericarp of A. trifoliata . Exogenous overexpression of the AtrANS increases and promotes the accumulation of anthocyanins and the expression of anthocyanin biosynthetic regulatory genes. Virus-induced gene silencing (VIGS) of the AtrANS resulted in the reduction of anthocyanin accumulation in the pericarp of A. trifoliata . In conclusion, our study revealed transcriptional events during pericarp coloration in A. trifoliata . Studies have also shown that AtrANS plays an important role in the regulation of anthocyanin biosynthesis.

Oxidative damage leading to loss of nutritional quality and pericarp discoloration of harvested litchi fruits drastically limits consumer acceptance and marketability. In the present investigation, the impact of postharvest melatonin application at different concentrations, i.e., 0.1 mM, 0.25 mM, and 0.5 mM, on fruit quality and shelf life of litchi fruits under cold storage conditions was studied. The results revealed the positive effect of melatonin application at all concentrations on fruit quality and shelf life. However, treatment with 0.5 mM concentration of melatonin resulted in minimum weight loss, decay loss, pericarp discoloration, and also retained higher levels of TSS, acidity, total sugar, ascorbic acid, anthocyanin, antioxidant, and phenolics content during cold storage. Melatonin administration also restricted the enzymatic activity of the polyphenol oxidase (PPO) and peroxidase (POD) enzymes in the fruit pericarp and maintained freshness of the fruits up to 30 days in cold storage. At the molecular level, a similar reduction in the expression of browning-associated genes, LcPPO, LcPOD , and Laccase, was detected in preserved litchi fruits treated with melatonin. Anthocyanin biosynthetic genes, LcUFGT and LcDFR , on the other hand showed enhanced expression in melatonin treated fruits compared to untreated fruits. Melatonin, owing to its antioxidant properties, when applied to harvested litchi fruits retained taste, nutritional quality and red color pericarp up till 30 days in cold storage.

Summary Changes in skin colour, as a visual cue for fruit ripeness, are important physiological markers in many crops including tomato, banana and grape. In kiwifruit, the skin remains brown during ripening, but de‐greening of the pericarp occurs to reveal accumulated carotenoids and anthocyanins in gold‐ and red‐fleshed cultivars. In this study, analysis of the inner and outer pericarp of Actinidia chinensis ‘Hongyang’ revealed faster chlorophyll degradation in the inner pericarp, compared with the outer pericarp. Based on transcriptome analysis, two chlorophyll degradation‐related genes encoding Mg‐dechelatases (AcSGR1 and AcSGR2) were more abundantly expressed in the inner pericarp, and this correlated with higher Mg‐dechelatase enzyme activity in the inner pericarp than in the outer pericarp. Weighted gene co‐expression network analysis identified potential regulators of AcSGR1/2. A differentially expressed NAM/ATAF/CUC transcription factor AcNAC2 was identified, which could directly interact with AcSGR1 and AcSGR2 promoters and strongly activate their expression. A closely related NAC, AcNAC3, also enhanced AcSGR1/2 expression, but was less abundantly expressed. Transient expression in tobacco confirmed that AcNAC2 and AcNAC3 promote chlorophyll degradation, and stable overexpression in kiwifruit verified that AcNAC2 acts via up‐regulation of AcSGR1/2 gene expression. CRISPR‐mediated knockouts of AcNAC2/3 in kiwifruit dramatically reduced expression levels of AcSGR1/2 genes in fruit, leading to significantly delayed chlorophyll degradation and de‐greening. Together, these results suggest that differential chlorophyll degradation drives the differences observed in chlorophyll content between the inner and outer pericarp of kiwifruit, which is principally modulated by the transcription factor AcNAC2.