GmNMH7基因在大豆成花诱导、花发育和开花逆转过程中的表达

The Expression Pattern of GmNMH7 Gene during Flowering Induction, Floral development and Flowering Reversion in Soybean

大豆 [Glycinemax (L )Merrill]是典型的短日照植物 ,光周期反应敏感品种在一定的短日 -长日条件下可发生开花逆转。本实验室以大豆品种自贡冬豆为材料 ,将SD (短日 )、LD (长日 )和SD13d -LD相结合 ,建立了大豆光周期反应机制研究的新的实验系统。本研究通过筛选自贡冬豆成熟花的cDNA文库得到MADS box基因家族的一个成员GmNMH7,采用RNA原位杂交技术分析了不同光周期条件下GmNMH7基因在大豆顶端分生组织分化过程中的表达 ,并观察了GmNMH7基因在幼叶、幼茎、根瘤等器官中的表达情况。主要结果总结如下 :在短日照 (SD)条件下 ,自贡冬豆植株可在较短时间内完成开花诱导、正常开花和结实。GmN MH7基因在可观察到的花芽分化出现之前即开始在大豆顶端分生组织中表达 ,其表达时间贯穿成花诱导、花芽分化、花器官发育及种子形成的全过程。在长日照 (LD)条件下 ,植株持续进行营养生长 ,没有任何形式的花器官出现 ,GmNMH7基因在顶端分生组织中一直不表达。在短日照 13天 -长日照 (SD13d -LD)条件下 ,6 0 %以上的植株出现花序逆转和花逆转 ,另一部分植株顶端出现短花序 ,开花期比持续短日处理的植株晚。在出现开花逆转的植株中 ,GmNMH7基因的表达可随长日处理日数的增加和营养器官的出现而减弱。

Soybean [ Glycine max (L ) Merrill] is a typical short day plant (SDP), and some photoperiod sensitive varieties can give rise to flowering reversion after the transfer from short days (SD) to long days (LD) In our laboratory, a novel experimental system consisting of 3 photoperiod treatments (SD, LD, SD13d LD) and developmental states (flowering, continuous vegetative growth, and flowering reversion) was established by using a late soybean variety Zigongdongdou (ZGDD) as material. This system can be used for studying the mechanism of photoperiod responses of SDP. In the present study, GmNMH7 , a soybean homologue of NMH7 gene, was cloned with plaque hybridization from ZGDD mature flower cDNA library by using MADS box conservative sequence as probe. The expression pattern of GmNMH7 in shoot apical meristem (SAM) of ZGDD under three different photoperiods was observed with RNA in situ hybridization. Similar work was also done in some young vegetative organs including trifoliate leaves, stems and nodules. Main results are summarized as follows: The flowering induction, floral initiation, blooming and fruiting of ZGDD plants were promoted by SD treatment. The expression of GmNMH7 could be detected in SAM before the observable floral formation, and during the course of flowering induction, differentiation and further development of floral organs, and seeds formation in soybean. In LD treatment, ZGDD plants kept their vegetative growth and did not produce any floral organs. No transcription of GmNMH7 was detected in SAM in LD condition before the end of the experiment. Inflorescence reversion was found in over 60% of plants and short terminal racemes were produced in other plants in SD13d LD treatment. All these plants bloomed much later than those in continuous SD. The amount of GmNMH7 transcripts in SAM was progressively reduced along with the increase of days of LD in plants that would produce reversed inflorescences. When SAM resumed to differentiate trifoliate leaves, no expression of GmNMH7 could still be detected. The expression of GmNMH7 in SAM was kept in SD13d LD plants with short terminal racemes but the amount was less than that in continuous SD. No distinctive and regular pattern of GmNMH7 expression was found in young trifoliate leaves, young stems, and nodules at certain developmental stages, possibly because of the limited data. The expression of GmNMH7 in these organs needs further investigation. Expression of GmNMH7 before the observable floral organogenesis provided an early evidence of flowering induction in soybean. The fact that GmNMH7 expression in SAM was controlled by photoperiods indicated that GmNMH7 gene might play some roles in flowering induction and floral development of soybean. We postulate that GmNMH7 functions like a meristem identity gene during the process of flowering and photoperiod responses in soybean. The results of this study also proved that the novel experimental system described above is effective and reliable for the study of photoperiodic responses and ontogeny of soybean.