Constitutive expression of the sunflower and chrysanthemum genes of the AP1/FUL group changes flowering timing in transgenic tobacco plants

Genome-Wide Identification of MADS-Box Family Genes in Safflower (Carthamus tinctorius L.) and Functional Analysis of CtMADS24 during Flowering

Safflower is an important economic crop with a plethora of industrial and medicinal applications around the world. The bioactive components of safflower petals are known to have pharmacological activity that promotes blood circulation and reduces blood stasis. However, fine-tuning the genetic mechanism of flower development in safflower is still required. In this study, we report the genome-wide identification of MADS-box transcription factors in safflower and the functional characterization of a putative CtMADS24 during vegetative and reproductive growth. In total, 77 members of MADS-box-encoding genes were identified from the safflower genome. The phylogenetic analysis divided CtMADS genes into two types and 15 subfamilies. Similarly, bioinformatic analysis, such as of conserved protein motifs, gene structures, and cis-regulatory elements, also revealed structural conservation of MADS-box genes in safflower. Furthermore, the differential expression pattern of CtMADS genes by RNA-seq data indicated that type II genes might play important regulatory roles in floral development. Similarly, the qRT-PCR analysis also revealed the transcript abundance of 12 CtMADS genes exhibiting tissue-specific expression in different flower organs. The nucleus-localized CtMADS24 of the AP1 subfamily was validated by transient transformation in tobacco using GFP translational fusion. Moreover, CtMADS24-overexpressed transgenic Arabidopsis exhibited early flowering and an abnormal phenotype, suggesting that CtMADS24 mediated the expression of genes involved in floral organ development. Taken together, these findings provide valuable information on the regulatory role of CtMADS24 during flower development in safflower and for the selection of important genes for future molecular breeding programs.

AfLFY, a LEAFY homolog in Argyranthemum frutescens, controls flowering time and leaf development

Flowering is important for plant propagation and survival, and it is also closely related to human life. Identifying the molecular mechanisms underlying flower development is essential for plant improvement and breeding. Flower development is a complex physiological process that is regulated by multiple genes. LFY genes play important roles in the floral meristem transition and act as crucial integrators in regulating the floral gene network. Argyranthemum frutescens is an ornamental species cultivated for floral displays, yet little is known about molecular mechanisms driving its flower development. In this study, the LEAFY gene homologue, AfLFY, was identified and cloned from A. frutescens, and its role and expression patterns were characterized. Two distinct copies of AfLFY were found in the A. frutescens genome and both sequences contained a 1248 bp open reading frame that encoded 415 amino acids. The putative protein sequences have a typical LFY family domain. In addition, AfLFY was expressed at the highest levels in young leaves of the vegetative stage and in the shoot apical bud meristem of the reproductive stage. Phylogenetic analysis showed that AfLFY was most closely related to DFL from Chrysanthemum lavandulifolium. Subcellular localization studies revealed that AfLFY localized to the nucleus. Heterologous expression of AfLFY in transgenic tobacco plants shortened its period of vegetative growth, converted the lateral meristems into terminal flowers and promoted precocious flowering. In addition, transgenic plants exhibited obvious morphological changes in leaf shape. qRT-PCR analysis indicated that the expression levels genes related to flowering, FT, SOC1, and AP1 were significantly upregulated in AfLFY transgenic plants. Our findings suggested that the AfLFY gene plays a vital role in promoting flowering and leaf development in A. frutescens. These results laid a foundation for us to understand the mechanism of AfLFY in regulation flowering, and the results will be helpful in improving A. frutescens through molecular breeding.

Ectopic expression of IiFUL isolated from Isatis indigotica could change the reproductive growth of Arabidopsis thaliana

The coding sequence of IiFUL in Isatis indigotica was isolated and was used in transformation of Arabidopsis. IiFUL overexpressing Arabidopsis plants exhibited early flowering phenotype, accompanied with the reduction of flower number and the production of terminal flower on the top of the main stems. In development process, the flowers located on the top of the main stems generated a lot of variations in phenotype, including abnormal swelling of pistil, withering and numerical change of stamens and petals, appearance of stigmatoid tissues and naked ovules at the margin or inside of sepals. Besides, secondary flower could be formed within the flowers on the top of the main stems. These observations illustrated that IiFUL mainly affected the development of inflorescence meristems and pistils, but its ectopic expression could also disturb the normal growth of other floral organs. Moreover, the fertile siliques produced by the lateral inflorescences of IiFUL overexpressing Arabidopsis plants showed indehiscent phenotype, and the shape of the cauline leaves was changed significantly. The results of quantitative real-time PCR revealed that higher transcriptional levels of IiFUL could be detected in flowers and silicles of I. indigotica. In comprehensive consideration of the previous reports about the dehiscence phenotype of Arabidopsis siliques and the fact that the siliques of IiFUL overexpressing Arabidopsis plants were indehiscent in the present work, it can be speculated that high expression of IiFUL in pericarp is likely the reason why the silicles of I. indigotica possess an indehiscent phenotype.