Screening And Analysis Of MADS-box Genes Related To Sunflower Lpm Mutants

In higher plant,flower development is a vital progress,and the key stage from vegetative growth to reproductive growth,thus it is necessary for plant reproduction to ensure the normal development of floral organs.Sunflower(Helianthus annuus.L.)is one of important oil crops in the world,and it is also popular as an ornamental plant in recent years.As typical plant of Compositae,studying the flower development of sunflower is significant to study the process of flower development for Compositae,and contributes to improve the yield of sunflower.MADA-box genes are important transcription factors with comprehensive functions in plant growth and development stage,especially during flower development.The research on MADS-box genes is mainly focused on model plant by far,but less in sunflower presently.In this paper,sunflower lpm(long petal mutant)was used for research material,and MADS-box candidate genes were screened from transcriptome database of sunflower flower development.The bioinformatic analysis of candidate genes were carried out,and their expression patterns were analyzed by quantitative Real-time PCR(qRT-PCR)in the wild type(WT)and lpm sunflower.The main results are as follows:(1)The results of morphological and anatomical observation showed that compared to the WT sunflower,ray florets were not significant difference,but petals were longer and stamens were degenerated in disc florets in the lpm sunflower.In the ray florets of lpm sunflower,petals began to prolong observably when 15 day prior to anthesis,whereas stamens began to degenerate when 25 day prior to anthesis.These results showed that 15 day and 25 day prior to anthesis are key stages for formation of lpm mutant character.(2)Histological observation showed that compared with WT sunflower,the cell size was no significant difference,but cell number was significantly more in the petal of lpm sunflower.The results suggested that the direct reason for the prolongation of petals in lpm is the increase in the number of petal cells.(3)Bioinformatics analysis of sunflower MADS-box genes showed that 25 MADS-box genes were identified,including 2 type? and 23 type? genes.The conserved motifs of type? MADS-box gene are more complete and the structure is more complex,which indicates that type? genes may have more complex functions than type? genes.Phylogenetic analysis showed that the 23 type? genes were unevenly distributed in 9 subfamilies,and the subgroup genes located in the same branch may have similar biological functions.(4)The tissue expression patterns of MADS-box genes showed that according to the expression of 23 type? genes in flowers,they can be classified as three expression types: The first was expressed specifically in flowers,the second was expressed in flowers and other tissues,and the third was expressed in other tissues except flowers.Most of the genes specifically expressed in flowers belong to floral development model genes.The results suggested that the floral development model gene of MADS-box gene may play an important role in sunflower flower development,and other MADS-box genes may play a certain role in other tissues.(5)The floral organ expression patterns of MADS-box genes showed that AP1/SQUA subfamily genes were mainly expressed in petals and bracts;PI/AP3 genes were mainly expressed in petals;AG genes were mainly expressed in pistil;while SEP subfamily genes were expressed in petals,pistils and other organs.The above results are basically consistent with the ABCE model,indicating that the flower development model is still applicable in sunflowers,which lays a foundation for the study of the molecular mechanism of flower organ determination and flower development in sunflowers.(6)Through the analysis of the expression of MADS-box genes in different flower development stages and flower organs,the results showed that the expression of B class gene HaMADS1 and E class gene HaMADS9 in lpm was up-regulated from 15 day prior to anthesis,and their expression was also significantly up-regulated in petals on the day of flowering.It is speculated that they may jointly affect the proliferation of petal cells and lead to petal prolongation.On the 15 day prior to anthesis,B class gene HaMADS13 and HaMADS19,C class gene Ha MADS2 and E class gene HaMADS12 in lpm flowers were significantly down-regulated,which suggested that they might be related to stamen degeneration.To sum up,in this paper it was identified the mutation traits and character formation period of lpm,and it was found that flower development model genes play an important role in the formation of lpm mutation character,especially B class genes.These results lay a foundation for the study of the molecular mechanism of sunflower flower development and provide a theoretical basis for directionally changing the agronomic characters of sunflower or other Compositae plants by means of molecular breeding or gene function in the future.