02657nas a2200157 4500008004100000245004500041210004400086520214200130653007502272100001802347700002302365700002202388700002302410700001702433856004902450 2002 eng d00aB-Class organ identity in basal monocots0 aBClass organ identity in basal monocots3 aIn basal monocots (e.g. Acoraceae, Alismatales s. APG 1998) it is difficult to unravel the ancestral features if floral morphology by comparison with their outgroups (magnoliids) and more derived clades of monocots. Two general types occur:1) flowers with distinct sepals and petals, often two or several whorls of stamens and carpels, and intercarpellary nectaries (e.g. Alismataceae, Butomaceae, Hydrocharitaceae, Tofieldiaceae);2) flowers with an undifferentiated perianth consisting of tepals, one or two whorls of carpels, which are often centrally fused and lack intercarpellary nectaries (e.g. Acoraceae, Araceae, Aponogetonaceae, Juncaginaceae, Potamogetonaceae, Scheuchzeriaceae).Type 1 is most similar to flowers in magnoliids such as Annonaceae, Aristolochiaceae, and monocots such as Dioscoreaceae and Liliaceae, whereas type 2 is similar to magnoliids such as Saururaceae and Chloranthaceae. In current phylogenetic analyses Acoraceae are sister to all other monocots, and Aponogetonaceae are basal within Alismatales. Therefore, the second type may represent a suite of morphologically plesiomorphic character states. However, because these basal clades stand on long branches, the actual features may as well have undergone extensive anagenesis, and therefore represent autapomorphies.To elucidate floral evolution in these basal monocots, a better understanding of perianth organ identity, differentiation and development is critical. Some of the genes responsible for the differentiation of the perianth are transcription factors of the MADS-box gene family, known as B-class genes: orthologs of APETALA3 and PISTILLATA in Arabidopsis, and DEFICIENS and GLOBULOSA in Antirrhinum. Expression of B-class genes in perianth organs of basal monocots exhibiting a morphologically undifferentiated perianth would be consistent with a petaloid developmental program for these organs, even though the perianth may appear bracteolar or sepalous in later stages of development. B-class genes in the genus Triglochin (Juncaginaceae) are characterized and the application of reverse transcription in situ PCR (RT-ISPCR) is discussed.10aflower development, MADS-box genes, monocots, organ identity, RT-ISPCR1 aBuzgo, Matyas1 aSoltis, Douglas, E1 aSoltis, Pamela, S1 aHauser, Bernard, A1 aJohansen, Bo uhttps://juncaginaceae.myspecies.info/node/5602748nas a2200313 4500008004100000245008200041210006900123300001200192490000700204520181600211653001302027653002202040653001902062653002802081653001802109653001802127653001302145653001902158653001502177100001802192700002302210700002202233700001702255700001302272700002302285700002202308700001702330856008702347 2006 eng d00aPerianth development in the basal monocot Triglochin maritima (Juncaginaceae)0 aPerianth development in the basal monocot Triglochin maritima Ju a107-1250 v223 a

Basal monocots exhibit considerable variation in inflorescence and floral structure. In some cases, such as Triglochin maritima, it is not clear whether the lateral and terminal structures of the inflorescence are flowers or pseudanthia, or where the limits between flowers and inflorescence lie. To address these questions, morphological studies were carried out, and the results show that in T. maritima both terminal and lateral structures are flowers, not pseudanthia. The terminal flower of T. maritima develops from the apical inflorescence meristem, suggesting that the apical meristem identity changes from ‘‘inflorescence’’ to ‘‘flower’’ during inflorescence development. In addition, distal flowers of T. maritima are reduced, and there is no distinct flower-subtending bract; instead, the perianth develops unidirectionally, resulting in an abaxial-median bract-like tepal and bilaterally symmetrical flowers, similar to those of other basal monocots, such as Aponogeton and Acorus. It is possible that the leaf primordium changes its positional homology from ‘‘flower-subtending bract’’ to ‘‘tepal.’’ Therefore, in some basal angiosperms with abbreviated development of lateral flowers the demarcation of the flower vs. the inflorescence is ontogenetically ambiguous. In situ hybridization experiments show that a putative ortholog of the B-class gene APETALA3 / DEFICIENS is expressed in developing stamens and carpels, and may also be expressed in the shoot axis of the very young inflorescence. This expression pattern seems to be consistent with the gradual transition between inflorescence and flower that was observed morphologically.

10aAPETALA310abasal angiosperms10afading borders10agene expression pattern10aJuncaginaceae10aMADS-box gene10amonocots10aorgan identity10aTriglochin1 aBuzgo, Matyas1 aSoltis, Douglas, E1 aSoltis, Pamela, S1 aKim, Sangtae1 aMa, Hong1 aHauser, Bernard, A1 aLeebens-Mack, Jim1 aJohansen, Bo uhttp://curis.ku.dk/ws/files/13860089/PERIANTH_DEVELOPMENT_IN_THE_BASAL_MONOCOT.pdf