Morphology and genetic development of flower in rice

flower development in rice

1. Morphology and genetic development of flower in rice Jatindra nath Mohanty, JRF

2. Information regarding rice Family – poaceae ( grass family) 12 chromosome 430Mb genome size, monocot Model plant due to its genetic resources, molecular tools, increasing information in genome project, genetic transformation is easy.

3. Morphology of rice flower

4. The ABCDE model in eudicots and expression patterns of rice MADS–box genes

5. Meristem transition: spikelet to floret FZP suppress axillaries meristem formation on the SM or promote FM identity. Both fzp and supernumerary bract ( snb ) mutants show repetitive production of rudimentary glumes . SNB and AP2 probably have functions in specifying FM identity in rice MIR 172 over expression targets this two to delay the transition SM to FM.

6. Lemma and palea development DROOPING LEAF (DL) is specifically expressed in the lemma. DL is a member of the YABBY gene family and controls leaf midrib formation and carpel specification in rice. MOSAIC FLORAL ORGANS1 (MFO1)/MADS6 is a member of the (AGL6) clade of MADS-box genes that specifies palea identity, along with lodicule identity, ovule development flower patterning, and FM determinacy in rice . (Known by mutant).

7. Contd ……….. REP1 TCP domain protein Palea primodia (later in lemma ,Stamen dev.) For both lemma and palea development group of genes are resp. AP1/FUL like gene. SEP/AGL 6,LOPSEP clade of gene (LHS), MADS15/DEP genes for normal function of both. OPB ZF protein AS2 & LOB protein normal lemma & palea dev.

8. Lodicule development In eudicot -petal dev contl . By class B(AP3, PI) Here in rice SPW-AP3 MADS2 MADS4-PI Loss of function of SPW1 cause transformation of the lodicule and the stamen into mrp - and carpel-like organs. Elongation of lodicules resultant in mutant of MADS 2. Lodicule devlopment

9. Stamen development All rice B-class genes, SPW1,MADS2, & MADS4, are required for the specification of the stamen as well as the lodicules. SPW1 mutant cause transformation from stamen to carpel-like organs.(AP3 orthologus ) MADS2 or MADS4 mutant causes apparently normal stamens(PI like gene) The C-class genes, rice MADS3 and MADS58, also show in stamen specification Mutant studies explain much more severe stamen to lodicules transformation.

10. Contd ……………. E-class SEP3 clade of genes, rice MADS7 and MADS8, are almost equally required for stamen specification. AGL6-like MFO1 regulates patterning of the stamens because mfo1 has a reduced number of stamens. Apart from the MADS-box genes, OPB involved in positively regulating B class function(SPW1,MADS2, & MADS4). In contrast, DL suppresses formation of stamens in whorl 4 by negatively regulating SPW1 expression.

11. Carpel development The C-class proteins form a tetramer with E-class proteins to exert carpel identity and FM determinacy in eudicot. Unlike eudicot in rice AG-like genes, MADS3 and MADS58, does not cause loss of carpel identity in rice. In whorl 4. whereas the mads3 mutants develop multiple carpel and MADS58 mutants causes an abnormal cup-shaped carpelloid.

12. Contd …….. Along with that a predicted, gene Os05g0203600 is closely related to C-class MADS-box genes, APO 1, DL, E-class protein SEP3, MADS 7 & 8 has role in both carpel identity and development. SEP3 indirectly helps in carpel identity by inducing class C gene function

13. Ovule development In Arabidopsis, the D-class gene SEEDSTICK (STK) is responsible for ovule specification. In rice, the D-class gene MADS13 is required for specification of ovule identity and FM identity known by reverse genetic way. Recently ,ovule is a lateral organ generated from the ovule founder region (OFR) through the action of MADS13 is known Result of Y2H system mark that ovule development also causes by MFO1 with MADS 13 complexly.

14. C onclusion Grass species are the major cereal crop in the whole world, so for major food in the increasing population depends on yielding of cereal grain. Thus, it is becoming more important to elucidate the genetic mechanism of grass flower development using rice as the model species. The structures and organization of perianth organs and the inflorescence are unique in rice. Spatial and temporal control of the meristem identity transition is key to determining the number and shape of the spikelet's in rice.

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