GENETIC CONTROL OF FLOWERING MECHANISM

Number of Flowers and fertility limit seed yield of seed plants. The results obtained from molecular analyses led to construct a simple model for flowering mechanism. The model (ABCDE) Implies 5 classes of genes control that mechanism. It was proposed that flowering takes place into 4 phases: the first is the appearance of plant response signals, the second is the appearance of flower organ identity. the third is activation of flower organ genes. and the fourth is the formation or flowering organ cells, However - time of flowering is supposed to pass via 4 pathways: the response to dark period, response to gibberellins. the autonomous function or the plant. and response to verbalization. There arc genes to specify vegetative meristems, and others to specify flowering meristems. The gene TFL1 controls vegetative c meristem, while AP(1) and LFY control the Flowering meristem. Signals of Flowering are controlled by a number of genes, such as; FLC1 and FT. The complementary action of FLC w ith FRI and PIE1 is important for flowering. The FLC codes for MADS proteins which are important For flowering, whereas, FLD represses transcription. VRN2 (of vernalization) controls FLC epigenctieally. The genes of the 5 classes of the model include (calss A), AP(1) and AP(2) that identify sepals and petals in whorls I and 2 of the: Flowcr,(class B), AP(3) and PI identify stamens in whorl 3, (class C)" AG identifies the pistil in whorl 4 and represses genes of class A. The class D includes STK ,SHP1,SHP2, related to shattering. The class E includes SEP1, SEP2 , SEP3 , FBP7 and FBP11 that control identity of placenta and ovule. Too many other loci have been found to be involved in flowering such as UFO, WUS, LUF, HEN, HUA, SAP, ANI, and others, Accordingly, mechanism of flowering is a complex syndrome looks like that of the seed yield of seed crops.