Li Zhang

Male sterility is crucial for solving pollen contamination and promoting inter-varietal hybridization. As the innermost layer of the anther, the tapetum directly contacts microspores, and tapetal abnormalities typically lead directly to male sterility. However, the regulatory mechanisms of tapetal degradation and its transport of substances to microspores remain poorly understood. This study identified LhMYB93 as a key positive regulator of tapetum degradation and microspore development in lilies. Specifically, transcriptomic analysis combined with transcriptomic and functional analyses revealed that LhMYB93 is expressed at lower levels in male-sterile lilies, and LhMYB93 can partially restore pollen fertility in male-sterile lilies. Additionally, LhMYB93 interacts with LhEAT1 to effectively activate the transcription of LhABCG26, a gene essential for tapetum degradation and microspore development. Additionally, in vitro and in vivo ubiquitination experiments have demonstrated that the LhEAT1–LhMYB93 module is ubiquitinated by the E3 ubiquitin ligase LhBRG3 during the late stages of anther development (S9–10) and subsequently degraded by the 26S proteasome. This process ensures the normal development and timely degradation of the tapetum, promoting the normal development of pollen. These findings provide novel insights into the regulatory mechanisms governing microspore development following tapetum degradation during lily anther development, expanding the regulatory framework of programmed cell death (PCD) and nutrient transport in tapetum during pollen development in monocotyledons.

Ethylene (ET) influences the synthesis of anthocyanins, although its regulatory effects can differ significantly across various plant species. In apples (Malus domestica), ET promotes anthocyanin synthesis, whereas in Arabidopsis thaliana, it inhibits its accumulation. Our research showed that ethephon (Eth), an ET derivative, promotes anthocyanin synthesis in ‘Viviana’ lilies, which has great potential in the cut flower industry. The regulatory mechanism whereby ET influences anthocyanin synthesis in lilies remains unclear. In this study, we screened and characterized an ET-induced ET response factors (ERFs), LvERF113, with inhibitory function. Our analyses suggested that LvERF113 could inhibit the negative regulatory function of LvMYB1 at transcriptional and posttranslational levels, promoting anthocyanin synthesis in ‘Viviana’ lily tepals. In addition, LvERF113 is positively regulated by LvMYB5, forming the LvMYB5-LvERF113-LvMYB1 module controlling anthocyanin synthesis by ET in ‘Viviana’ lily. These findings offer new insights into the ET regulatory network of anthocyanin synthesis and provide a theoretical basis for the application of ET derivatives in the cut flower industry.

Salt stress is a major abiotic stress that interferes with plant growth and affects crop production. Dehydrin (DHN), a member of the late embryogenesis abundant (LEA) protein family, was considered to be a stress protein involved in the protective reaction of plant dehydration. Our previous research has shown that overexpression of the Suaeda salsa SsDHN gene enhances tolerance to salt stress in tobacco. However, the research on its protection in photosynthesis under salt stress remains unclear. In this study, gene overexpression (SsDHN-OE) tobacco plants were utilized to study the effect of the SsDHN gene on plant photosynthesis under salt stress. Our findings showed that overexpression of SsDHN increased the biomass, leaf area, root length, and root surface area in tobacco seedlings under salt stress conditions. The transgenic tobacco with overexpression of SsDHN had obvious stomatal closure, which effectively alleviated the adverse effects of salt stress on photosynthetic efficiency. Overexpression of the SsDHN gene in tobacco can effectively reduce the degree of photoinhibition and chloroplast damage caused by salt stress. Moreover, the SsDHN-overexpressing transgenic tobacco plants exhibited a decrease in oxidative damage and protected membrane structures related to photosynthesis by increasing antioxidant enzyme activity and antioxidant substance content. It was further found that the expression levels of photosynthetic and antioxidant-related genes Rubisco, SBPase, POD7, CAT3, APX2, and SOD3 were significantly up-regulated by overexpressing the SsDHN gene in tobacco seedlings under salt stress. In conclusion, the SsDHN gene might improve the salt stress resistance of tobacco seedlings and be involved in regulating photosynthesis and antioxidant activity under salt stress.

Lily (Lilium spp.), a horticultural crop serving both ornamental and edible functions, derives its coloration primarily from anthocyanins. However, limited studies have been conducted on the accumulation of anthocyanins within lilies. In this study, we cloned a light-induced transcription factor named as LvBBX24 in lilies. Through genetic and biochemical analysis, we determined that LvBBX24 could upregulate the transcription of LvMYB5 and facilitate anthocyanin synthesis. Moreover, we identified that darkness promoted the degradation of LvBBX24 protein. Through screening a yeast library, we identified LvbZIP44 acts as its interacting partner. Genetic testing confirmed that LvbZIP44 also plays a role in promoting lily anthocyanin synthesis. This indicates a potential synergistic regulatory effect between LvBBX24 and LvbZIP44. Our study indicates that LvBBX24 and LvbZIP44 cooperate to regulate anthocyanin accumulation in lily petals. These findings provide compelling evidence supporting the idea that LvBBX24 and LvbZIP44 may form a looped helix surrounding the LvMYB5 promoter region to regulate anthocyanin biosynthesis.

Low temperatures can inhibit plant growth and development and reduce fruit yield. This study demonstrated that the expression of AnGolS1 from Ammopiptanthus nanus (A. nanus) encoding a galactinol synthase enhanced tomato cold tolerance. In AnGolS1-overexpressing plants, the jasmonic acid (JA) biosynthesis substrates 13-hydroperoxylinolenicacid and 12,13-epoxylinolenicacid were significantly accumulated, and the expression levels of the ethylene response factor (SlERF4-7) and serine protease inhibitor (SlSPI5) were increased. We speculated that there may be correlations among galactinol, ethylene signaling, the protease inhibitor, protease, and JA levels. The expression levels of SlERF4-7 and SlSPI5 as well as the JA content were significantly increased under exogenous galactinol treatment. Additionally, the expression of SlSPI5 was reduced in SlERF4-7-silenced plants, and SlERF4-7 was confirmed to bind to the dehydration-responsive element (DRE) of the SlSPI5 promoter. These results suggest that SlSPI5 is a target gene of the SlERF4-7 transcription factor. In addition, SlSPI5 interacted with cysteine protease (SlCPase), while SlCPase interacted with lipoxygenase (SlLOX5) and allene oxide synthase (SlAOS2). When SlCPase was silenced, JA levels increased and plant cold tolerance was enhanced. Therefore, galactinol regulates JA biosynthesis to enhance tomato cold tolerance through the SlERF4-7-SlSPI5-SlCPase-SlLOX5/SlAOS2 model. Overall, our study provides new perspectives on the role of galactinol in the JA regulatory network in plant adaptation to low-temperature stress.

Tomato is a horticultural crop with an incomplete flavonoid metabolic pathway that does not typically accumulate anthocyanins in the fruit. In recent years, intensive studies of the loci Anthocyanin fruit (Aft) and atroviolacium (atv) have clarified the functions of positive regulators (R2R3-MYBs) and a negative regulator (CPC-MYB) in anthocyanin biosynthesis in the fruits. However, little is known about the R2R3-MYB repressors. Here, we used transient overexpression analysis to show that SlMYB7, a subgroup 4 AtMYB4-like R2R3-MYB, inhibited anthocyanin accumulation and reduced expression of anthocyanin synthase genes in the 'black pearl' tomato fruits, which usually accumulate high concentrations of anthocyanins. These findings revealed that SlMYB7 served as a repressor of anthocyanin production. Furthermore, SlMYB7 actively repressed SlANS expression by binding its promoter and passively inhibited anthocyanin synthesis by interacting with the basic helix-loop-helix (bHLH) proteins SlJAF13 and SlAN1, which are involved in the formation of MBW complexes. Thus, SlMYB7 and the MBW complex may coregulate the anthocyanin content of 'black pearl' tomato fruits via a negative feedback loop. These findings provide a theoretical basis for the future enhancement of tomato anthocyanin contents through genetic manipulation of the biosynthetic regulatory network.

Dehydrins (DHNs) play crucial roles in a broad spectrum of abiotic stresses in model plants. However, the evolutionary role of DHNs has not been explored, and the function of DHN proteins is largely unknown in Ammopiptanthus nanus (A. nanus), an ancient and endangered legume species from the deserts of northwestern China. In this study, we isolated a drought-response gene (c195333_g1_i1) from a drought-induced RNA-seq library of A. nanus. Evolutionary bioinformatics showed that c195333_g1_i1 is an ortholog of Arabidopsis DHN, and we renamed it AnDHN. Moreover, DHN proteins may define a class of proteins that are evolutionarily conserved in all angiosperms that have experienced a contraction during the evolution of legumes. Arabidopsis plants overexpressing AnDHN exhibited morpho-physiological changes, such as an increased germination rate, higher relative water content (RWC), higher proline (PRO) content, increased peroxidase (POD) and catalase (CAT) activities, lower contents of malondialdehyde (MDA), H₂O₂ and O₂^–, and longer root length. Our results showed that the transgenic lines had improved drought resistance with deep root system architecture, excellent water retention, increased osmotic adjustment, and enhanced reactive oxygen species (ROS) scavenging. Furthermore, the transgenic lines also had enhanced salt and cold tolerance. Our findings demonstrate that AnDHN may be a good candidate gene for improving abiotic stress tolerance in crops.Key Message: Using transcriptome analysis in Ammopiptanthus nanus, we isolated a drought-responsive gene, AnDHN, that plays a key role in enhancing abiotic stress tolerance in plants, with strong functional diversification in legumes.

Flower color is one of the most important qualitative characteristics of ornamental horticultural plants, which mainly depends on anthocyanins and carotenoids. Modification of flower color in ornamental plants involves many aspects, including complicated structural gens, transcription factors and metabolic pathways. Anthocyanins are important secondary metabolites in the flavonoid biosynthesis pathway, which mainly derive from six anthocyanidins. Anthocyanin has antioxidant activity, protects plants and performs some other functions. Studying the genes and regulatory factors in the biosynthesis pathway will contribute to cultivating novel flower color plants and to improving plants’ resistance. To date, a series of structural and regulatory genes that are involved in anthocyanin synthesis and color formation have been reported, whose functions have also been revealed. Some color-related transgenic flowers have been successfully obtained. Carotenoids are the source of the yellow pigments in the petals of many flowers. The carotenoid biosynthesis pathway as well as its major enzymes and genes are conducive to regulate its biosynthesis via genetic engineering methods and thereby changing the color of flowers. In this paper, we review the plant flower color in terms of mechanisms of plant pigment formation, classification of flower color, biosynthesis pathway, and genes related to anthocyanin formation. Subsequently, we analyze the regulating mechanism of the expression of these genes, including transcription regulation and post-transcription regulation. The methods and achievements in flower color improvement in recent years are summarized. Finally, analyzing the molecular regulatory network in flower color formation provides a theoretical basis for the improvement and modification of flower color.

Background: Petals are the colorful region of many ornamental plants. Quality traits of petal color directly affect the value of ornamental plants. Although the regulatory mechanism of flower color has been widely studied in many plants, that of lily flower color is still worth further exploration.Results: In this study, the pigmentation regulatory network in different regions of the petal of lily cultivar ‘Vivian’ was analyzed through tissue structure, metabolites biosynthesis, and gene expression. We found that cell morphology of the petal in un-pigmented region differed from that in pigmented region. The cell morphology tends to flatten in un-pigmented region where the color is lighter. Moreover, high level anthocyanin was found in the pigmented regions by metabonomic analysis, especially cyanidin derivatives. However, flavanones were accumulated, contrast with anthocyanin in the un-pigmented regions of lily petal. To understand the relationship of these different metabolites and lily flower color, RNA-Seq was used to analyze the differentially expressed genes-related metabolite biosynthesis. Among these genes, the expression levels of several genes-related cyanidin derivatives biosynthesis were significantly different between the pigmented and un-pigmented regions, such asLvMYB5, LvMYB7, LvF3’H, LvDFR, LvANSandLv3GT.Conclusions: This data will help us to further understand the regulation network of lily petal pigmentation and create different unique color species.