Isolation And Expression Analysis Of The Marker Genes Related To Somatic Embryogenesis Of Liriodendron Hybrids (L.Chinense (Hemsl.)Sarg. XL. Tulipifera L.)

Liriodendron Hybrids is the inter-species hybrid between L.chinense(Hemsl.) Sarg. and L.tuipifera L. which are the last two exist species of Liriodendron in the world,and become an important urban afforestation tree species. To the date, people can master the large scale vegetative propagation technique of Liriodendron Hybrids through somatic embryogenesis (SE), but its molecular mechanism was seldom reported.we have successfully cloned several SE-related genes by degenerate primers that would be useful in markering different type of cells in the process of"vegetative to embryonic"transition of Liriodendron Hybrids. That includes: the LhL1L encoding the HAP3 subunit of CCAAT box-binding factor(CBF); the LhFUS3 encoding B3 domain transcription factors(TF); the WUS-like homeobox genes LhWOX1 and LhWOX4; the knotted-like homeobox genes LhKN1 and LhKN2; LhSERK1 and LhSERK2 with high similarity to carrot Somatic Embryogenesis Receptor like Kinase gene; LhFER1 and LhFER2 mediating reception male-female interactions during plant fertilization; five members of polyubiquitin gene LhUBI1-5;as well as LhEXP1 encoding one expansion in Liriodendron Hybrids.Through the expression analysis of those so-called SE marker genes, we have found that LhL1L is strongly expressed in the young and tender petiole and the embryonic callus, thus LhL1L presumably can marker the predetermined embryonic cell which remains in the immature petiole after seek germination. LhFUS3 expression is suppressed in all the vegetative organs except for the high level induced expression in embryonic callus(EC),which indicates that the LhFUS3 is embryo-specific TF gene. LhWOX1 is also preferentially expressed in immature petiole, so LhWOX1 and LhL1L may cooperate in regulating the immature state of cells or development of the petiole.LhKN1 can be highly expressed in both shoot apical meristem (SAM) and the mature stem, revealing that there is overlapping mechanisms regulating the SAM and the vascular cambium, consistent with the hypothesis about populous ARK1.Since the expression signals is gradually stronger among non-embryonic callus I (NECI), non-embryonic callus II(NECII) and EC, it might suggest that LhKN1 functions as maintaining the stem cells in SAM and helps to keep the multi-potential capability of certain type cells in vivo. LhKN2 and LhWOX4 have similar roles in keeping the ?undifferentiated state of the NECII cells. Cloning and expression analysis of the SE-related genes of Liriodendron Hybrids will make a good preparation for exploring the molecular mechanism in the transition of"somatic vegetative cell-undifferentiated cell-embryonic cell".