microRNA172 targets APETALA2 to regulate flavonoid biosynthesis in apple (Malus domestica)

Genome-wide analyses of the GbAP2 subfamily reveal the function of GbTOE1a in salt and drought stress tolerance in Ginkgo biloba

The APETALA2 (AP2) transcription factors play crucial roles in plant growth and stage transition. Ginkgo biloba is an important medicinal plant renowned for the rich flavonoid content in its leaves. In this study, 18 GbAP2s were identified from the G. biloba genome and classified into three clusters. We found that the members of the euAP2 cluster, including four TOEs (GbTOE1a/1b/1c/3), exhibited a higher expression level in most samples compared to other members. Specifically, GbTOE1a may have a positive regulatory role in salt and drought stress responses. The overexpression of GbTOE1a in G. biloba calli resulted in a significant increase in the flavonoid content and upregulation of flavonoid biosynthesis genes, including PAL, 4CL, CHS, F3H, FLSs, F3'Hs, OMT, and DFRs. By contrast, the silencing of GbTOE1a in seedlings decreased the flavonoid content and the expression of flavonoid synthesizing genes. In addition, the silenced seedlings exhibited decreased antioxidant levels and a higher sensitivity to salt and drought treatments, suggesting a crucial role of GbTOE1a in G. biloba salt and drought tolerance. To the best of our knowledge, this was the first investigation into the identification and characterization of GbAP2s in G. biloba. Our results lay a foundation for further research on the regulatory role of the AP2 family in flavonoid synthesis and stress responses.

VvERF117 positively regulates grape cold tolerance through direct regulation of the antioxidative gene BAS1

Cold stress significantly threatens grape quality, yield, and geographical distribution. Although ethylene-responsive factors (ERFs) are recognized for their pivotal roles in cold stress, the regulatory mechanisms of many ERFs contributing to tolerance remain unclear. In this study, we identified the cold-responsive gene VvERF117 and elucidated its positive regulatory function in cold tolerance. VvERF117 exhibits transcriptional activity and localizes to the nucleus. VvERF117 overexpression improved cold tolerance in transgenic Arabidopsis, grape calli, and grape leaves, whereas VvERF117 silencing increased cold sensitivity in grape calli and leaves. Furthermore, VvERF117 overexpression remarkably upregulated the expression of several stress-related genes. Importantly, BAS1, encoding a 2-Cys peroxidase (POD), was confirmed as a direct target gene of VvERF117. Meanwhile, compared to the wild-type, POD activity and H2O2 content were remarkably increased and decreased in VvERF117-overexpressing grape calli and leaves, respectively. Conversely, VvERF117 silencing displayed the opposite trend in grape calli and leaves under cold stress. These findings indicate that VvERF117 plays a positive role in cold resistance by, at least in part, enhancing antioxidant capacity through regulating the POD-encoding gene VvBAS1, leading to effective mitigation of reactive oxygen species.

Exploring the regulatory role of non-coding RNAs in fiber development and direct regulation of GhKCR2 in the fatty acid metabolic pathway in upland cotton

Cotton fiber holds immense importance as the primary raw material for the textile industry. Consequently, comprehending the regulatory mechanisms governing fiber development is pivotal for enhancing fiber quality. Our study aimed to construct a regulatory network of competing endogenous RNAs (ceRNAs) and assess the impact of non-coding RNAs on gene expression throughout fiber development. Through whole transcriptome data analysis, we identified differentially expressed genes (DEGs) regulated by non-coding RNA (ncRNA) that were predominantly enriched in phenylpropanoid biosynthesis and the fatty acid elongation pathway. This analysis involved two contrasting phenotypic materials (J02-508 and ZRI015) at five stages of fiber development. Additionally, we conducted a detailed analysis of genes involved in fatty acid elongation, including KCS, KCR, HACD, ECR, and ACOT, to unveil the factors contributing to the variation in fatty acid elongation between J02-508 and ZRI015. Through the integration of histochemical GUS staining, dual luciferase assay experiments, and correlation analysis of expression levels during fiber development stages for lncRNA MSTRG.44818.23 (MST23) and GhKCR2, we elucidated that MST23 positively regulates GhKCR2 expression in the fatty acid elongation pathway. This identification provides valuable insights into the molecular mechanisms underlying fiber development, emphasizing the intricate interplay between non-coding RNAs and protein-coding genes.

Transcriptional regulation of flavonol biosynthesis in plants

Flavonols are a class of flavonoids that play a crucial role in regulating plant growth and promoting stress resistance. They are also important dietary components in horticultural crops due to their benefits for human health. In past decades, research on the transcriptional regulation of flavonol biosynthesis in plants has increased rapidly. This review summarizes recent progress in flavonol-specific transcriptional regulation in plants, encompassing characterization of different categories of transcription factors (TFs) and microRNAs as well as elucidation of different transcriptional mechanisms, including direct and cascade transcriptional regulation. Direct transcriptional regulation involves TFs, such as MYB, AP2/ERF, and WRKY, which can directly target the key flavonol synthase gene or other early genes in flavonoid biosynthesis. In addition, different regulation modules in cascade transcriptional regulation involve microRNAs targeting TFs, regulation between activators, interaction between activators and repressors, and degradation of activators or repressors induced by UV-B light or plant hormones. Such sophisticated regulation of the flavonol biosynthetic pathway in response to UV-B radiation or hormones may allow plants to fine-tune flavonol homeostasis, thereby balancing plant growth and stress responses in a timely manner. Based on orchestrated regulation, molecular design strategies will be applied to breed horticultural crops with excellent health-promoting effects and high resistance.

T2T reference genome assembly and genome-wide association study reveal the genetic basis of Chinese bayberry fruit quality

Chinese bayberry (Myrica rubra or Morella rubra; 2n = 16) produces fruit with a distinctive flavor, high nutritional, and economic value. However, previous versions of the bayberry genome lack sequence continuity. Moreover, to date, no large-scale germplasm resource association analysis has examined the allelic and genetic variations determining fruit quality traits. Therefore, in this study, we assembled a telomere-to-telomere (T2T) gap-free reference genome for the cultivar 'Zaojia' using PacBio HiFi long reads. The resulting 292.60 Mb T2T genome, revealed 8 centromeric regions, 15 telomeres, and 28 345 genes. This represents a substantial improvement in the genome continuity and integrity of Chinese bayberry. Subsequently, we re-sequenced 173 accessions, identifying 6 649 674 single nucleotide polymorphisms (SNPs). Further, the phenotypic analyses of 29 fruit quality-related traits enabled a genome-wide association study (GWAS), which identified 1937 SNPs and 1039 genes significantly associated with 28 traits. An SNP cluster pertinent to fruit color was identified on Chr6: 3407532 to 5 153 151 bp region, harboring two MYB genes (MrChr6G07650 and MrChr6G07660), exhibiting differential expression in extreme phenotype transcriptomes, linked to anthocyanin synthesis. An adjacent, closely linked gene, MrChr6G07670 (MLP-like protein), harbored an exonic missense variant and was shown to increase anthocyanin production in tobacco leaves tenfold. This SNP cluster, potentially a quantitative trait locus (QTL), collectively regulates bayberry fruit color. In conclusion, our study presented a complete reference genome, uncovered a suite of allelic variations related to fruit-quality traits, and identified functional genes that could be harnessed to enhance fruit quality and breeding efficiency of bayberries.

Genome-wide identification of the Pinus tabuliformis CONSTANS-like gene family and their potential roles in reproductive cone development

The CONSTANS-like (COL) genes, as a core transcription factor in the photoperiod regulation pathway, play a key role in plant reproduction development. However, their molecular characterization has rarely been studied in Pinus tabuliformis. Here, 10 PtCOL genes were identified in the P. tabuliformis genome and multiple sequence alignments have indicated that the PtCOL proteins contained highly conserved B-BOX1 and CCT domains. Sequence similarity analysis showed that PtCOL1 and PtCOL3 had the higher similarity with Norway spruce COLs (PaCOL2 and PaCOL1) and Arabidopsis COLs (AtCOL3, 4 and 5), respectively. Phylogeny and gene structure analyses revealed that PtCOLs were divided into three subgroups, each with identical or similar distributions of exons, introns, and motifs. Moreover, 10 PtCOLs were distributed on 6 chromosomes and PtCOL9 has syntenic gene pairs in both Ginkgo biloba and Sequoiadendron giganteum. Interestingly, in transcriptome profiles, most PtCOLs exhibited a diurnal oscillation pattern under both long (LD) and short (SD) day conditions. Additionally, PtCOLs were highly expressed in needles and female cones, and showed different spatial expression patterns. Among the ten PtCOLs, PtCOL1/3 heterologous overexpression Arabidopsis displayed a delayed-flowering phenotype under SD, indicating that they are likely to play a crucial role in the reproductive development. Additionally, PtCOL1 and PtCOL3 were not only capable of interacting with each other, but they were each capable of interacting with themselves. Furthermore, PtCOL1 and PtCOL3 were also involved in the MADS-box protein-protein interaction (PPI) network in P. tabuliformis cone development. Direct interactions of PtDAL11 with PtCOL1/3 impeded PtCOL1/3 translocation into the nucleus. In summary, this study provided comprehensive understanding for the functions of the PtCOL gene family and revealed their biological roles in the photoperiod-dependent P. tabuliformis cone development.

The ncRNAs Involved in the Regulation of Abiotic Stress-Induced Anthocyanin Biosynthesis in Plants

Plants have evolved complicated defense and adaptive systems to grow in various abiotic stress environments such as drought, cold, and salinity. Anthocyanins belong to the secondary metabolites of flavonoids with strong antioxidant activity in response to various abiotic stress and enhance stress tolerance. Anthocyanin accumulation often accompanies the resistance to abiotic stress in plants to scavenge reactive oxygen species (ROS). Recent research evidence showed that many regulatory pathways such as osmoregulation, antioxidant response, plant hormone response, photosynthesis, and respiration regulation are involved in plant adaption to stress. However, the molecular regulatory mechanisms involved in controlling anthocyanin biosynthesis in relation to abiotic stress response have remained obscure. Here, we summarize the current research progress of specific regulators including small RNAs, and lncRNAs involved in the molecular regulation of abiotic stress-induced anthocyanin biosynthesis. In addition, an integrated regulatory network of anthocyanin biosynthesis controlled by microRNAs (miRNAs), long non-coding RNAs (lncRNAs), transcription factors, and stress response factors is also discussed. Understanding molecular mechanisms of anthocyanin biosynthesis for ROS scavenging in various abiotic stress responses will benefit us for resistance breeding in crop plants.

Isoenzymes of the Flavonoid and Phenylpropanoid Pathways Show Organ-Specific Regulation during Apple Fruit Development

Elucidating the molecular mechanisms controlling fruit development is a primary target for the improvement of new apple (Malus × domestica Borkh.) cultivars. The first two weeks of development following pollination are crucial to determine fruit characteristics. During this period, a lot of changes take place in apple fruit, going from rapid cell division to the production of important metabolites. In this work, attention was focused on the phenylpropanoid and flavonoid pathways responsible for the production of numerous compounds contributing to fruit quality, such as flavonols, catechins, dihydrochalcones and anthocyanins. A total of 17 isoenzymes were identified, belonging to seven classes of the phenylpropanoid and flavonoid pathways that, despite showing more than 80% sequence identity, showed differential expression regulation during the first two weeks of apple fruit development. This feature seems to be quite common for most of the enzymes of both pathways. Differential regulation of isoenzymes was shown to be present in both 'Golden Delicious' and a wild relative (Malus mandshurica), even though differences were also present. Each isoenzyme showed a specific pattern of expression in the flower and fruit organs, suggesting that genes coding for enzymes with the same function may control different aspects of plant biology. Finally, promoter analysis was performed in order to highlight differences in the number and type of regulatory motifs. Overall, our results indicate that the control of the expression of genes involved in the phenylpropanoid and flavonoid pathways may be very complex as not only enzymes belonging to the same class, but even putative isoenzymes, can have different roles for the plant. Such genes may represent an important regulatory mechanism, as they would allow the plant to fine-tune the processing of metabolic intermediates towards different branches of the pathway, for example, in an organ-specific way.

Small RNA and Degradome Sequencing Reveal Roles of miRNAs in the Petal Color Fading of Malus Crabapple

The Malus crabapple is an important woody ornamental plant. The fading of petals during its development significantly affects their ornamental value. Petal color is related to anthocyanin content and miRNAs play an important role in the post-transcriptional regulation of anthocyanin synthesis. However, the mechanisms underlying miRNA regulation of petal fading have rarely been studied. Transcriptome and small RNA sequencing of petals from the blooming phases of Malus. 'Indian Summer' varieties S1 (small bud), S2 (initial-flowering), and S3 (late-flowering) allowed us to identify 230 known miRNAs and 17 novel miRNAs, including 52 differentially expressed miRNAs which targeted 494 genes and formed 823 miRNA-target pairs. Based on the target gene annotation results, miRNA-target pairs were screened that may be involved in the fading process of Malus crabapple petals through three different pathways: anthocyanin synthesis, transport, and degradation, involving mcr-miR858-MYB1\MYB5 and mcr-miR396-McCHI inhibiting anthocyanin synthesis; mcr-miR167, mcr-miR390, mcr-miR535, and mcr-miR858 inhibiting anthocyanin transport from the cytoplasm to the vacuole by targeting ABC transporter genes (ABCB, ABCC, ABCD, and ABCG); and mcr-miR398 targeting the superoxide dismutase genes (CZSOD2 and CCS) to accelerate anthocyanin degradation. These findings offer a novel approach to understanding the mechanism of petal fading and serve as a reference for other plants with floral fading.

Anthocyanins distribution, transcriptional regulation, epigenetic and post-translational modification in fruits

Anthocyanins have indispensable functions in plant resistance, human health, and fruit coloring, which arouse people's favorite. It has been reported that anthocyanins are widely found in fruits, and can be affected by numerous factors. In this review, we systematically summarize anthocyanin functions, classifications, distributions, biosynthesis, decoration, transportation, transcriptional regulation, DNA methylation, and post-translational regulation in fruits.

Metabolome, Plant Hormone, and Transcriptome Analyses Reveal the Mechanism of Spatial Accumulation Pattern of Anthocyanins in Peach Flesh

Anthocyanins are important secondary metabolites in fruits, and anthocyanin accumulation in the flesh of peach exhibits a spatial pattern, but the relevant mechanism is still unknown. In this study, the yellow-fleshed peach, cv. 'Jinxiu', with anthocyanin accumulation in the mesocarp around the stone was used as the experimental material. Red flesh (RF) and yellow flesh (YF) were sampled separately for flavonoid metabolite (mainly anthocyanins), plant hormone, and transcriptome analyses. The results showed that the red coloration in the mesocarp was due to the accumulation of cyanidin-3-O-glucoside, with an up-regulation of anthocyanin biosynthetic genes (F3H, F3'H, DFR, and ANS), transportation gene GST, and regulatory genes (MYB10.1 and bHLH3). Eleven ERFs, nine WRKYs, and eight NACs were also defined as the candidate regulators of anthocyanin biosynthesis in peach via RNA-seq. Auxin, cytokinin, abscisic acid (ABA), salicylic acid (SA), and 1-aminocyclopropane-1-carboxylic acid (ACC, ethylene precursor) were enriched in the peach flesh, with auxin, cytokinin, ACC, and SA being highly accumulated in the RF, but ABA was mainly distributed in the YF. The activators and repressors in the auxin and cytokinin signaling transduction pathways were mostly up-regulated and down-regulated, respectively. Our results provide new insights into the regulation of spatial accumulation pattern of anthocyanins in peach flesh.

A comparative analysis of small RNA sequencing data in tubers of purple potato and its red mutant reveals small RNA regulation in anthocyanin biosynthesis

Anthocyanins are a group of natural pigments acting as stress protectants induced by biotic/abiotic stress in plants. Although the metabolic pathway of anthocyanin has been studied in potato, the roles of miRNAs on the metabolic pathway remain unclear. In this study, a purple tetraploid potato of SD92 and its red mutant of SD140 were selected to explore the regulation mechanism of miRNA in anthocyanin biosynthesis. A comparative analysis of small RNAs between SD92 and SD140 revealed that there were 179 differentially expressed miRNAs, including 65 up- and 114 down-regulated miRNAs. Furthermore, 31 differentially expressed miRNAs were predicted to potentially regulate 305 target genes. KEGG pathway enrichment analysis for these target genes showed that plant hormone signal transduction pathway and plant-pathogen interaction pathway were significantly enriched. The correlation analysis of miRNA sequencing data and transcriptome data showed that there were 140 negative regulatory miRNA-mRNA pairs. The miRNAs included miR171 family, miR172 family, miR530b_4 and novel_mir170. The mRNAs encoded transcription factors, hormone response factors and protein kinases. All these results indicated that miRNAs might regulate anthocyanin biosynthesis through transcription factors, hormone response factors and protein kinase.

Kaempferol-3-rhamnoside overaccumulation in flavonoid 3'-hydroxylase tt7 mutants compromises seed coat outer integument differentiation and seed longevity

Seeds slowly accumulate damage during storage, which ultimately results in germination failure. The seed coat protects the embryo from the external environment, and its composition is critical for seed longevity. Flavonols accumulate in the outer integument. The link between flavonol composition and outer integument development has not been explored. Genetic, molecular and ultrastructural assays on loss-of-function mutants of the flavonoid biosynthesis pathway were used to study the effect of altered flavonoid composition on seed coat development and seed longevity. Controlled deterioration assays indicate that loss of function of the flavonoid 3' hydroxylase gene TT7 dramatically affects seed longevity and seed coat development. Outer integument differentiation is compromised from 9 d after pollination in tt7 developing seeds, resulting in a defective suberin layer and incomplete degradation of seed coat starch. These distinctive phenotypes are not shared by other mutants showing abnormal flavonoid composition. Genetic analysis indicates that overaccumulation of kaempferol-3-rhamnoside is mainly responsible for the observed phenotypes. Expression profiling suggests that multiple cellular processes are altered in the tt7 mutant. Overaccumulation of kaempferol-3-rhamnoside in the seed coat compromises normal seed coat development. This observation positions TRANSPARENT TESTA 7 and the UGT78D1 glycosyltransferase, catalysing flavonol 3-O-rhamnosylation, as essential players in the modulation of seed longevity.

Overview of Repressive miRNA Regulation by Short Tandem Target Mimic (STTM): Applications and Impact on Plant Biology

The application of miRNA mimic technology for silencing mature miRNA began in 2007. This technique originated from the discovery of the INDUCED BY PHOSPHATE STARVATION 1 (IPS1) gene, which was found to be a competitive mimic that prevents the cleavage of the targeted mRNA by miRNA inhibition at the post-transcriptional level. To date, various studies have been conducted to understand the molecular mimic mechanism and to improve the efficiency of this technology. As a result, several mimic tools have been developed: target mimicry (TM), short tandem target mimic (STTM), and molecular sponges (SPs). STTM is the most-developed tool due to its stability and effectiveness in decoying miRNA. This review discusses the application of STTM technology on the loss-of-function studies of miRNA and members from diverse plant species. A modified STTM approach for studying the function of miRNA with spatial-temporal expression under the control of specific promoters is further explored. STTM technology will enhance our understanding of the miRNA activity in plant-tissue-specific development and stress responses for applications in improving plant traits via miRNA regulation.

Coordinating Diverse Functions of miRNA and lncRNA in Fleshy Fruit

Non-coding RNAs play vital roles in the diverse biological processes of plants, and they are becoming key topics in horticulture research. In particular, miRNAs and long non-coding RNAs (lncRNAs) are receiving increased attention in fruit crops. Recent studies in horticulture research provide both genetic and molecular evidence that miRNAs and lncRNAs regulate biological function and stress responses during fruit development. Here, we summarize multiple regulatory modules of miRNAs and lncRNAs and their biological roles in fruit sets and stress responses, which would guide the development of molecular breeding techniques on horticultural crops.

A banana transcriptional repressor MaAP2a participates in fruit starch degradation during postharvest ripening

Fruit postharvest ripening is a crucial course for many fruits with significant conversion of biosubstance, which forms an intricate regulatory network. Ethylene facilitates the ripening process in banana with a remarkable change of fruit starch, but the mechanism adjusting the expression of starch degradation-related enzyme genes is incompletely discovered. Here, we describe a banana APETALA2 transcription factor (MaAP2a) identified as a transcriptional repressor with its powerful transcriptional inhibitory activity. The transcriptional level of MaAP2a gradually decreased with the transition of banana fruit ripening, suggesting a passive role of MaAP2a in banana fruit ripening. Moreover, MaAP2a is a classic nucleoprotein and encompasses transcriptional repressor domain (EAR, LxLxLx). More specifically, protein-DNA interaction assays found that MaAP2a repressed the expression of 15 starch degradation-related genes comprising MaGWD1, MaPWD1, MaSEX4, MaLSF1, MaBAM1-MaBAM3, MaAMY2B/2C/3A/3C, MaMEX1/2, and MapGlcT2-1/2-2 via binding to the GCC-box or AT-rich motif of their promoters. Overall, these results reveal an original MaAP2a-mediated negative regulatory network involved in banana postharvest starch breakdown, which advances our cognition on banana fruit ripening and offers additional reference values for banana varietal improvement.

MicroRNAs: emerging regulators in horticultural crops

Horticulture is one of the oldest agricultural practices with great popularity throughout the world. Horticultural crops include fruits, vegetables, ornamental plants, as well as medicinal and beverage plants. They are cultivated for food, specific nutrition, and medical use, or for aesthetic pleasure. MicroRNAs (miRNAs), which constitute a major class of endogenous small RNAs in plants, affect a multitude of developmental and physiological processes by imparting sequence specificity to gene regulation. Over the past decade, tens of thousands of miRNAs have been identified in more than 100 horticultural crops and their critical roles in regulating quality development of diverse horticultural crops have been demonstrated. Here, we review how miRNAs have emerged as important regulators and promising tools for horticultural crop improvement.

Recent Developments and Strategies for the Application of Agrobacterium-Mediated Transformation of Apple Malus × domestica Borkh

Genetic transformation has become an important tool in plant genome research over the last three decades. This applies not only to model plants such as Arabidopsis thaliana but also increasingly to cultivated plants, where the establishment of transformation methods could still pose many problems. One of such plants is the apple (Malus spp.), the most important fruit of the temperate climate zone. Although the genetic transformation of apple using Agrobacterium tumefaciens has been possible since 1989, only a few research groups worldwide have successfully applied this technology, and efficiency remains poor. Nevertheless, there have been some developments, especially in recent years, which allowed for the expansion of the toolbox of breeders and breeding researchers. This review article attempts to summarize recent developments in the Agrobacterium-mediated transformation strategies of apple. In addition to the use of different tissues and media for transformation, agroinfiltration, as well as pre-transformation with a Baby boom transcription factor are notable successes that have improved transformation efficiency in apple. Further, we highlight targeted gene silencing applications. Besides the classical strategies of RNAi-based silencing by stable transformation with hairpin gene constructs, optimized protocols for virus-induced gene silencing (VIGS) and artificial micro RNAs (amiRNAs) have emerged as powerful technologies for silencing genes of interest. Success has also been achieved in establishing methods for targeted genome editing (GE). For example, it was recently possible for the first time to generate a homohistont GE line into which a biallelic mutation was specifically inserted in a target gene. In addition to these methods, which are primarily aimed at increasing transformation efficiency, improving the precision of genetic modification and reducing the time required, methods are also discussed in which genetically modified plants are used for breeding purposes. In particular, the current state of the rapid crop cycle breeding system and its applications will be presented.

APETALA2/ethylene responsive factor in fruit ripening: Roles, interactions and expression regulation

Insects and animals are attracted to, and feed on ripe fruit, thereby promoting seed dispersal. As a vital vitamin and nutrient source, fruit make up an indispensable and enjoyable component of the human diet. Fruit ripening involves a series of physiological and biochemical changes in, among others, pigmentation, chlorophyll (Chl) degradation, texture, sugar accumulation, and flavor. Growing evidence indicates that the coordinated and ordered trait changes during fruit ripening depend on a complex regulatory network consisting of transcription factors, co-regulators, hormonal signals, and epigenetic modifications. As one of the predominant transcription factor families in plants and a downstream component of ethylene signaling, more and more studies are showing that APETALA2/ethylene responsive factor (AP2/ERF) family transcription factors act as critical regulators in fruit ripening. In this review, we focus on the regulatory mechanisms of AP2/ERFs in fruit ripening, and in particular the recent results on their target genes and co-regulators. We summarize and discuss the role of AP2/ERFs in the formation of key fruit-ripening attributes, the enactment of their regulatory mechanisms by interaction with other proteins, their role in the orchestration of phytohormone-signaling networks, and the epigenetic modifications associated with their gene expression. Our aim is to provide a multidimensional perspective on the regulatory mechanisms of AP2/ERFs in fruit ripening, and a reference for understanding and furthering research on the roles of AP2/ERF in fruit ripening.