QTL analysis of early flowering of female flowers in zucchini(Cucurbita pepo L.)

Early flowering promotes early maturity, production, and the capacity to counteract biotic and abiotic stresses, making it an important agronomic trait in zucchini. The present study demonstrated that the zucchini inbred line ‘19’ consistently flowered early, taking significantly fewer days to bloom the first female flower(DFF) than the inbred line ‘113’. Genetic analysis revealed that DFF, an inheritable quantitative trait, is controlled by multiple genes. Based on the strategy of quantitative trait locus(QTL) sequencing(QTL-seq) combined with linkage analysis, three QTLs for DFF were identified on chromosomes 4, 11, and 20. This study used additional F2 populations grown under different environmental conditions for QTL mapping analysis of DFF with insertion/deletion(InDel) markers to validate these results. Using the composite interval mapping(CIM) method of R/qtl software, we only identified one major locus under all environmental conditions, located in a 117-kb candidate region on chromosome 20. Based on gene annotation, gene sequence alignment, and qRT-PCR analysis, we found that the Cp4.1LG20g08050 gene encoding a RING finger protein may be a candidate gene for the opposite regulation of early flowering in zucchini. In summary, these results lay a foundation for a better understanding of early flowering and improving early flowering-based breeding strategies in zucchini.

Transformation of Tobacco with Two AP1 Genes Isolated from Poplar( Populus simonii × Populus nigra)

[ Objective ] This study aimed to analyze the functions of AP1 gene from Populus simonii × Populus nigra and to lay the theoretical foundation for shortening the breeding cycle of forest trees and investigating the flowering mechanism in poplar. [ Method] Plant expression vectors of AP1 genes were constructed and transformed into tobacco leaf disks with Agrobacterium-mediated method. Transgenic tobacco plants were identified by PCR. [ Result] AP1 genes were integrated into the genome of tobacco. Transgenic tobacco plants all presented an early flowering phenotype compared with wild-type tobacco. [ Conclusion] AP1 genes could promote early flowering in transgenic tobacco plants, which provided theoretical basis for molecular regulation of flowering in poplar.

GmNF-YC4 delays soybean flowering and maturation by directly repressing GmFT2a and GmFT5a expression

Flowering time and growth period are key agronomic traits which directly affect soybean(Glycine max(L.)Merr.)adaptation to diverse latitudes and farming systems.The FLOWERING LOCUS T(FT)homologs GmFT2a and GmFT5a integrate multiple flowering regulation pathways and significantly advance flowering and maturity in soybean.Pinpointing the genes responsible for regulating GmFT2a and GmFT5a will improve our understanding of the molecular mechanisms governing growth period in soybean.In this study,we identified the Nuclear Factor Y-C(NFY-C)protein GmNF-YC4 as a novel flowering suppressor in soybean under long-day(LD)conditions.GmNF-YC4 delays flowering and maturation by directly repressing the expression of GmFT2a and GmFT5a.In addition,we found that a strong selective sweep event occurred in the chromosomal region harboring the GmNF-YC4 gene during soybean domestication.The GmNF-YC4Hap3 allele was mainly found in wild soybean(Glycine soja Siebold&Zucc.)and has been eliminated from G.max landraces and improved cultivars,which predominantly contain the GmNF-YC4Hap1 allele.Furthermore,the Gmnf-yc4 mutants displayed notably accelerated flowering and maturation under LD conditions.These alleles may prove to be valuable genetic resources for enhancing soybean adaptability to higher latitudes.

Evolutionary assessment of SQUAMOSA PROMOTER BINDING PROTEIN‑LIKE genes in citrus relatives with a specific focus on flowering

Phase transition and floral induction in citrus requires several years of juvenility after germination.Such a long period of juvenility has been a major hindrance to its genetic improvement program.Studies have shown that miR156 along with its downstream genes SQUAMOSA PROMOTER BINDING PROTEINS(SBP)and SBP-LIKE(SPL)mediate the phase transition and floral induction process in plants.Our current study has systematically analyzed SPLs in 15 different citrus-related species,systematically annotated them based on their close homology to their respective Arabidopsis orthologs,and confirmed the functional attributes of the selected members in floral precocity.The majority of the species harbored 15 SPLs.Their cis-element assessment suggested the involvement of the SPLs in diverse developmental and physiological processes in response to different biotic and abiotic cues.Among all,SPL5,SPL9,and SPL11 stood out as consistently differentially expressed SPLs in the adult and young tissues of different citrusrelated species.Independent overexpression of their F.hindsii orthologs(FhSPL5,FhSPL9,and FhSPL11)brought an enhanced expression of endogenous FLOWERING LOCUS T leading to the significantly precocious flowering in transgenic Arabidopsis lines.Future study of the genes in the citrus plant itself is expected to conclude the assessments made in the current study.

Temporal and Spatial Requirement of EMF1 Activity for Arabidopsis Vegetative and Reproductive Development

EMBRYONIC FLOWER （EMF） genes are required to maintain vegetative development via repression of flower homeotic genes in Arabidopsis. Removal of EMF gene function caused plants to flower upon germination, producing abnormal and sterile flowers. The pleiotropic effect of ernfl mutation suggests its requirement for gene programs involved in diverse developmental processes. Transgenic plants harboring EMF1 promoter：：glucuronidase （GUS） reporter gene were generated to investigate the temporal and spatial expression pattern of EMF1. These plants displayed differential GUS activity in vegetative and flower tissues, consistent with the role of EMF1 in regulating multiple gene programs. EMFI：：GUS expression pattern in emf mutants suggests organ-specific auto-regulation. Sense- and antisense （as） EMF1 cDNA were expressed under the control of stage- and tissue-specific promoters in transgenic plants. Characterization of these transgenic plants showed that EMF1 activity is required in meristematic as well as differentiating tissues to rescue emf mutant phenotype. Temporal removal or reduction of EMF1 activity in the embryo or shoot apex of wild-type seedlings was sufficient to cause early flowering and terminal flower formation in adult plants. Such reproductive cell memory is reflected in the flower MADS-box gene activity expressed prior to flowering in these early flowering plants. However, temporal removal of EMF1 activity in flower meristem did not affect flower development. Our results are consistent with EMF1＇s primary role in repressing flowering in order to allow for vegetative growth.