Morphological Characteristics Of Spikelet And Expression Of Related Genes In Rice Double Mutant Osmads6-5+eg1-3

The development of rice floral organ is a complicated biological process controlled by many floral development genes.The known results show that both OsMADS6 and EG1 are two key genes of regulating rice floral formation.Now,we found the null alleles of OsMADS6 and EG1,OsMADS6-5(Osmads6-5)and EG1-3(egl-3).Inside Osmads6-5 floret,all floral organs but lemma homeoticaly transformed into glume-like organs and its floral determinacy lost;The floral determinacy of eg 1-3 floret also lost and four whorls of floral organs have changed.All inner stamens,pistils and lodicules degenerated,which were replaced by extra symmetric glumes in the prolonged receptacle.To further clarify the interaction of the both genes and their functional mechanism,in this study,the morphological characteristics,expressional level of some related floral organ identity genes and their functions of Osmads6-5+eg1-3,were analyzed.The results are as follows:1.The morphological characteristics of Osmads6-5+eg1-3The floret of Osmads6-5+eg1-3 exhibited a strong mutant phenotype.The magority of lemma and palea of Osmads6-5+eg1-3 florets could develop normally,but minor palea became small.Inside the floret,lodicule was replaced by glume-like organs and stamen and pistil disapeared completely,which were replaced by the structure "Spikelets in Flower" with the prolonged receptacle.Its floral meristem determinacy lost.Interestingly,these central extra spikelets were wrapped by some extra symmetric glumes and it is similar to egl-3.The results of paraffin section show that more vascular bundles lead to a typical open-hull phenotype.The results of SEM show that the initiation of both lemma and palea primordium could occur normally,which is similar to wild type.The initiation of the lodicule primordium is as same as wild type,but in the later phase,the lodicule developed rapidly leading to glume-like organs formation;Stamen and pistil didn’t differentiate.In the central region,some receptacle primordiums were formatted leading to the prolonged receptacles with some spikelet primordiums.In the end,these spikelet primordiums developed to spikelets wrapped by the extra glume-like organs.2.The relationship of EGl-3,OsMADS6-5 and some other floral organ identity genesIn order to clarify the relationship of EGI-3,OsMADS6-5 and some other floral organ identity genes,in this study,the expressional level of several B-class,C-class,E-class and Zin-finger genes in two single mutants or the double mutant was analyzed by qRT-PCR.The results show that OsMADS 16/3/1/7 were down regulated obviously in Osmads6-5+eg1-3.The result show that OsMADS6-5 and EG1-3 could control the development of rice floral organs individually or together and the down regulation of B-class and C-class genes resulted in the loss of inner three whorls’ floral meristem identity;OsMADS6-5 and EG1-3 were up regulated in Osmads6-5,down regulated in eg1-3.The results show that OsMADS6-5 and EG1-3 could regulate the rice floral development in different order;EG1-3 was up regulated in Osmads6-5.It shows that OsMADS6-5 could regulate the expression of EG1-3 negatively;The results of situ hybridization show that the expressional pattern of EG1-3 in Osmads6-5 is similar to the wild type’s.In a word,both OsMADS6-5 and EG1-3 are two key genes to control rice floral development.Thy both can regulate rice four whorls’ floral organs development by affecting the expressional level of other floral organ identity genes.During the rice floral developmental process,OsMADS6-5 and EG1-3 can control the floral development individually or together in different order.