Cloning And Expression Analysis Of The Flowering Related Genes In Pineapple(Ananas Comosus)

Pineapple[Ananas comosus(Linn.)Merr.]is one of the three most important herbaceous fruit trees in the tropics.According to the data from FAO in 2016,65600 hectares of pineapple was planted in China,with a total output of 1.551 million tons.Some scholars have recently focused on the pineapple flowering,and only a few genes related to flowering in pineapple have been reported.In this study,five genes related to the flowering of ’Tarinon 16’ pineapple were cloned including AcSOC1,AcFT,AcSEP3,AcAGL6,AcLFY,and the expression profiles of these five genes were studied In addition,we also studied the morphological and anatomical characteristics in thr prosess of pineapple flowering.All the data will lay the foundation for elucidating the mechnisms of flowering in pineapple.1)According to the morphological changes of growth cone,the differentiation process of the pineapple flower buds was divided in three stages:flower induction stage,flower initiation stage and flower organ development stage.At the stage of flowering induction,the leaves at the top of pineapple stalks began to get smaller,and the young red inflorescence began to come out.At the stage of flowering initiation,the plants grew the inflorescence.When the plant turned into the stage of floral organ development,it can also be divided into three stages:At the initial flowering stage,the pineapple inflorescence germinated some of purple floets,and 1-2 florets opened in the base of the inflorescence.At the full-bloom stage,1-2 layers of florets in the middle of inflorescence were open,and when the temperature high,3-4 layers of floets were open at the same time.About final flowering,all the florets in inflorescence were open while the petals wilted,dried or even fell off.Throughout the flowering period,all the florets bloomed in the order from base to top,and the whole process from rip-panel to blossom fall in floet was not more than a day.In the early stage of reproductive growth,the apex of the primordia began to form a semi oval growing point,and subsequently the apical growth point of the primordia gradually presented a regular cone(which can be called the growth cone)and closed to the center until the vascular bundles of growing cone became deeper and biggerand the flower organs developed.2)AcSOCl gene encodes a protein with 208 amino acids,which has a highly conservative MADS-box structure domain at the N-terminal and a conserved DVETELFIGLP region at the non-conservative C-terminal.Real-time fluorescence quantitative PCR analysis showed that acetylene could induced the expression of AcSOCl gene in pineapple,and the amount of its expression was the highest on the sixth day after treatment,and then decreased.The expression levels of AcSOCl gene in different tissues and organs of pineapple were significantly different,in which the expression was the highest in the mature leaves,and the lowest at the late stage of flower development.2)Ac FT gene encodes a protein with 178 amino acids,containg a conserved LYN/IYN triplets of the FT-like family with a conserved fragment B which can promote flowering in plants.Real-time fluorescence quantitative PCR analysis showed that acetylene could induce the expression of AcFT gene in pineapple,and the amount of its expression was the highest in the first day after treatment,and then decreased.In the natural flowering process of pineapple,the expression of AcFT gene expression became its peak when the apical leaves became red.There were significant differences in the expression of AcFT gene in different tissues and organs of pineapple,in which the expression of AcFT gene was the highest in pineapple fruits at the later stage of flower development and the lowest in leaves.3)AcSEP3 gene encodes a protein with 246 amino acids,which has a highly conserved 5’-terminal MADS domains and semi-conserved K domains.The specific SEP I and SEP Ⅱ motifs in SEP-like protein are found at the 3’ terminal of AcSEP3 protein.Real-time fluorescence quantitative PCR analysis showed that acetylene could induce the expression of AcSEP3 gene in pineapple,and the amount was the highest on the 50 day after treatments.The expression of AcSEP3 gene reached its peak after full bloom in the natural flowering process of pineapple.There were significant differences in the expression of AcSEP3 gene in different tissues and organs of pineapple,and the highest expression level was found in the fruits at the later stage of flower development.4)AcAGL6 gene encodes a protein with 241 amino acids and belongs to the AGL6 gene of AGL6 subgroup in MADS-box gene family.Real-time fluorescence quantitative PCR analysis showed that acetylene could induce the expression of AcAGL6 gene in pineapple,and the expression level was the highest on the 45 day after treatment.There were significant differences in the expression of AcAGL6 gene in different tissues and organs of pineapple,in which the highest expression level was found in the flower primordia,and little in the vegetative tissues such as leaves,stems and so on.5)AcLFY gene encodes a protein with 366 amino acids,in which contains a proline rich region at the 5o-N terminal,leucine repeats,basic and acidic domains,and has the typical structural characteristics of the FLO/LEAFY family.Real-time fluorescence quantitative PCR analysis showed that acetylene could induce the expression of AcLFY gene,and the expression level was the highest on the 40th day after treatment,and then decreased.In the natural flowering process of pineapple,the expression of AcLFY gene reached its peak when the florets in the middle of inflorescence bloomed.There were significant differences in the expression of AcLFY gene in different tissues and organs of pineapple,in which the expression of AcLFY gone was the highest in terminal buds and the lowest in roots.6)Combined with the results in the model plant Arabidopsis thaliana and the data in this study,it is inferred that both AcSOCl and AcFT are closely related to the flowering,and involved in the flowering induction in pineapple.AcSEP3 gene is involved in the development of pineapple floral organs,AcAGL6 gene plays the important roles in floral bud differentiation and floral organ development in pineapple.AcLFY gene is involved in the formation of pineapple inflorescence and also plays an important role in the transformation from the vegetative growth to reproductive growth or from stem meristem into flower meristem in pineapple.