Physic nut (Jatropha curcas L.) has attracted extensive attention because of its fast growth, easy reproduction, tolerance to barren conditions, and high oil content of seeds. SWEET (Sugar Will Eventually be Exported Transporter) family genes contribute to regulating the distribution of carbohydrates in plants and have great potential in improving yield and stress tolerance. In this study, we performed a functional analysis of the homology of these genes from physic nut, JcSWEET12 and JcSWEET17a. Subcellular localization indicated that the JcSWEET12 protein is localized on the plasma membrane and the JcSWEET17a protein on the vacuolar membrane. The overexpression of JcSWEET12 (OE12) and JcSWEET17a (OE17a) in Arabidopsis leads to late and early flowering, respectively, compared to the wild-type plants. The transgenic OE12 seedlings, but not OE17a, exhibit increased salt tolerance. In addition, OE12 plants attain greater plant height and greater shoot dry weight than the wild-type plants at maturity. Together, our results indicate that JcSWEET12 and JcSWEET17a play different roles in the regulation of flowering time and salt stress response, providing a novel genetic resource for future improvement in physic nut and other plants.

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BACKGROUND: The SET domain group (SDG) genes encode histone lysine methyltransferases, which regulate gene transcription by altering chromatin structure and play pivotal roles in plant flowering determination. However, few studies have investigated their role in the regulation of flowering in upland cotton.
RESULTS: A total of 86 SDG genes were identified through genome-wide analysis in upland cotton (Gossypium hirsutum). These genes were unevenly distributed across 25 chromosomes. Cluster analysis revealed that the 86 GhSDGs were divided into seven main branches. RNA-seq data and qRT‒PCR analysis revealed that lysine methyltransferase 3 (KMT3) genes were expressed at high levels in stamens, pistils and other floral organs. Using virus-induced gene silencing (VIGS), functional characterization of GhKMT3;1a and GhKMT3;2a revealed that, compared with those of the controls, the GhKMT3;1a- and GhKMT3;2a-silenced plants exhibited later budding and flowering and lower plant heightwere shorter. In addition, the expression of flowering-related genes (GhAP1, GhSOC1 and GhFT) significantly decreased and the expression level of GhSVP significantly increased in the GhKMT3;1a- and GhKMT3;2a-silenced plants compared with the control plants.
CONCLUSIONS: A total of 86 SDG genes were identified in upland cotton, among which GhKMT3;1a and GhKMT3;2a might regulate flowering by affecting the expression of GhAP1, GhSOC1, GhFT and GhSVP. These findings will provide genetic resources for advanced molecular breeding in the future.

OBJECTIVE: As winter and spring temperatures continue to increase, the timing of flowering and leaf out is advancing in many seasonally cold regions. This advancement could put plants that flower early in the spring at risk of decreased reproduction in years when there are late freeze events. Unfortunately, relatively little is known about floral freezing tolerance in forest communities. In this study, we examined the impact of freezing temperatures on the flowers of woody plants in a region where there is rapid winter warming in North America.
METHODS: We subjected the flowers of twenty-five woody species to a hard (-5ºC) and a light freeze (0ºC). We assessed tissue damage using electrolyte leakage. In a subset of species, we also examined the impact of a hard freeze on pollen tube growth. To determine if the vulnerability of flowers to freezing damage relates to flowering time and to examine the responsiveness of flowering time to spring temperature, we recorded the date of first flower for our study species for three years.
CONCLUSIONS: Across species, we found that floral freezing tolerance was strongly tied to flowering time with the highest freezing tolerance occurring in plants that bloomed earlier in the year. We hypothesize that these early blooming species are unlikely to be impacted by a false spring. Instead, the most vulnerable species to a false spring should be those that bloom later in the season. The flowering time in these species is also more sensitive to temperature, putting them at a great risk of experiencing a false spring. Ultimately, floral damage in one year will not have a large impact on species fitness, but if false springs become more frequent, there could be long-term impacts on reproduction of vulnerable species.

The sunflower (Helianthus annuus L.) is one of the most essential oil crops in the world. Several component traits, including flowering time, plant height, stem diameter, seed weight, and kernel weight, determine sunflower seed and oil yield. Although the genetic mechanisms governing the variation of these yield-related traits have been studied using various approaches, genome-wide association studies (GWAS) have not been widely applied to sunflowers. In this study, a set of 342 sunflower accessions was evaluated in 2019 and 2020 using an incomplete randomized block design, and GWAS was conducted utilizing two complementary approaches: the mixed linear model (MLM) and the fixed and random model circulating probability unification (farmCPU) model by fitting 226,779 high-quality SNPs. As a result, GWAS identified a number of trait-associated SNPs. Those SNPs were located close to several genes that may serve as a basis for further molecular characterization and provide promising targets for sunflower yield improvement.

The improvement of performance and yield in both cultivar and species mixtures has been well established. Despite the clear benefits of crop mixtures to agriculture, identifying the critical mechanisms behind performance increases are largely lacking. We experimentally demonstrated that the benefits of rice cultivar mixtures were linked to relatedness-mediated intraspecific neighbour recognition and discrimination under both field and controlled conditions. We then tested biochemical mechanisms of responses in incubation experiments involving the addition of root exudates and a root-secreted signal, (-)-loliolide, followed by transcriptome analysis. We found that closely related cultivar mixtures increased grain yields by modifying root behaviour and accelerating flowering over distantly related mixtures. Importantly, these responses were accompanied by altered concentration of signalling (-)-loliolide that affected rice transcriptome profiling, directly regulating root growth and flowering gene expression. These findings suggest that beneficial crop combinations may be generated a-priori by manipulating neighbour genetic relatedness in rice cultivar mixtures and that root-secreted (-)-loliolide functions as a key mediator of genetic relatedness interactions. The ability of relatedness discrimination to regulate rice flowering and yield raises an intriguing possibility to increase crop production.

Immunity and flowering are energy-consuming processes. However, the mechanism underlying the balance between immunity and flowering remains to be elucidated. Here, we report that the E3 ligase ideal plant architecture 1 interactor 1 (IPI1) controls rice immunity and flowering via two different pathways, one dependent on and another independent of its E3 ligase activity. We found that IPI1, a RING-finger E3 ligase, interacts with another E3 ligase, AvrPiz-t-interacting protein 6 (APIP6), and protects APIP6 from degradation by preventing APIP6\'s self-ubiquitination. Stabilization of APIP6 by IPI1 requires no IPI1 E3 ligase activity and leads to degradation of APIP6 substrates via the ubiquitin-proteasome system (UPS). Meanwhile, IPI1 directly ubiquitinates OsELF3-1 and OsELF3-2, two homologs of EARLY FLOWERING3 (ELF3), targeting them for degradation via the 26S proteasome. IPI1 knockout plants display early flowering but compromised resistance to rice blast. Thus, IPI1 balances rice immunity and flowering via both E3 ligase-dependent and -independent pathways.

Flowering time is a crucial adaptive response to seasonal variation in plants and is regulated by environmental cues such as photoperiod and temperature. In this study, we demonstrated the regulatory function of rice CRYPTOCHROME-INTERACTING BASIC HELIX-LOOP-HELIX 1-LIKE (OsCIBL1) in flowering time. Overexpression of OsCIB1L promoted flowering, whereas the oscib1l knockout mutation did not alter flowering time independent of photoperiodic conditions. Cryptochromes (CRYs) are blue light photoreceptors that enable plants to sense photoperiodic changes. OsCIBL1 interacted with OsCRY2, a member of the rice CRY family (OsCRY1a, OsCRY1b, and OsCRY2), and bound to the Early heading date 1 (Ehd1) promoter, activating the rice-specific Ehd1-Heading date 3a/RICE FLOWERING LOCUS T 1 pathway for flowering induction. Dual-luciferase reporter assays showed that the OsCIBL1-OsCRY2 complex required blue light to induce Ehd1 transcription. Natural alleles resulting from nonsynonymous single nucleotide polymorphisms in OsCIB1L and OsCRY2 may contribute to the adaptive expansion of rice cultivation areas. These results expand our understanding of the molecular mechanisms controlling rice flowering and highlight the importance of blue light-responsive genes in the geographic distribution of rice.

Monocarpic senescence, characterized by whole-plant senescence following a single flowering phase, is widespread in seed plants, particularly in crops, determining seed harvest time and quality. However, how external and internal signals are systemically integrated into monocarpic senescence remains largely unknown. Here, we report that the Arabidopsis thaliana transcription factor WRKY1 plays essential roles in multiple key steps of monocarpic senescence. WRKY1 expression is induced by age, salicylic acid (SA), and nitrogen (N) deficiency. Flowering and leaf senescence are accelerated in the WRKY1 overexpression lines but are delayed in the wrky1 mutants. The combined DNA affinity purification sequencing and RNA sequencing analyses uncover the direct target genes of WRKY1. Further studies show that WRKY1 coordinately regulates three processes in monocarpic senescence: (1) suppressing FLOWERING LOCUS C gene expression to initiate flowering, (2) inducing SA biosynthesis genes to promote leaf senescence, and (3) activating the N assimilation and transport genes to trigger N remobilization. In summary, our study reveals how one stress-responsive transcription factor, WRKY1, integrates flowering, leaf senescence, and N remobilization processes into monocarpic senescence, providing important insights into plant lifetime regulation.

Luffa spp. is an important worldwide cultivated vegetable and medicinal plant from the Cucurbitaceae family. In this study, we report a high-quality chromosome-level genome of the high-generation inbred line SG261 of Luffa acutangula. The genomic sequence was determined by PacBio long reads, Hi-C sequencing reads, and 10× Genomics sequencing, with an assembly size of 739.82 Mb, contig N50 of 18.38 Mb, and scaffold N50 of 56.08 Mb. The genome of L. acutangula SG261 was predicted to contain 27,312 protein-coding genes and 72.56% repetitive sequences, of which long terminal repeats (LTRs) were an important form of repetitive sequences, accounting for 67.84% of the genome. Phylogenetic analysis reveals that L. acutangula evolved later than Luffa cylindrica, and Luffa is closely related to Momodica charantia. Comparing the genome of L. acutangula SG261 and L. cylindrica with PacBio data, 67,128 high-quality structural variations (SVs) and 55,978 presence-absence variations (PAVs) were identified in SG261, resulting in 2424 and 1094 genes with variation in the CDS region, respectively, and there are 287 identical genes affected by two different structural variation analyses. In addition, we found that the transcription factor FY (FLOWERING LOCUS Y) families had a large expansion in L. acutangula SG261 (flowering in the morning) compared to L. cylindrica (flowering in the afternoon), which may result in the early flowering time in L. acutangula SG261. This study provides valuable reference for the breeding of and pan-genome research into Luffa species.