Physiology of flowering plant Molecular level

Physiology of flowering plant Molecular level

lecular studies on flowering c Basic knowledge genes, gene expression profile control of gene expression Practical aspect e.g. breeding/improvement

Flowering shoot apex Induction to Initiation to Specificat Vegetative to Reproductive Indeterminate to Determina Shoot apical meristem to Inflorescence meristem Floral meristem (primord

Flowering Signal Hormone Temperature Photoperiod Autonomous environment/endogenous

al stimulus production ollowing inducing signal owering switch to turn on origen of flowering commitment hoot apex: require sufficient amount stimulus for continuous flower prod af: commit to continuously producti stimulus (irreversible)

Florigen: shoot apex or leaf mpatiens purple flower Short day for flowering 5 SD: flowering SD to LD: continue flowering SD remove leaves to LD: leaves with purple petals to

igen: shoot apex or leaf tiens red flower hort day for flowering : flowering rn to LD: vegetative stage at inner ire continuous supply of inducing si

ering genes expressed in youn Maize: intermediate Arabidopsis: constans

enes in Flower Development tructural gene Flower organ Flower color Flower scent egulatory gene Protein product involved in contro expression of other genes Via protein-DNA interaction

Flowering genes Timing Meristem identity Organ identity

Approaches Flowering mutant Gene identification Transformation Mutant complementation

Why flowering? utionary diversification of organisms Alteration of developmental events ation in structure and regulation of g ontrolling developmental mechanism

Why flowering? wers: invariant pattern and organiz Perianth/Reproductive organs Varied number, size and position

Flowering genes model: Arabidopsis and Snapdragon on characteristics: ral-specific expression with differen entified as homeotic genes ntrol specification of meristem and organ identity of flower

Flowering genes asses: meristem identity genes eg, LFY CAL AP1 organ identity genes eg, AP2 AP3 PI AG t genes encode proteins with homologous regions of 260 amino uence similarity : common ancestor

Flowering genes hly conserved region about 57 amino alled MADS box also found in yeast and human ulatory gene family: transcription fa S box gene in other crops: omato tobacco potato petunia

eotic gene: identity of organs/body pattern and position ence-specific DNA-binding moiety: nimal: homeodomain (homeobox gen lant leaf: homeodomain protein oral organ: MADS box protein / gene

Meristem identity genes tem: SAM (indeterminate) for s IM (indeterminate) for infloresc FM (determinate) for flower

Meristem identity genes orescence meristem Mutant: early flowering in Arabidopsi onversion of IM to FM erminal flower fl FL protein Negative regulator of LFY and AP gen

Meristem identity genes oral meristem Mutant: partial conversion of FM to Leafy in Arabidopsis Floricaula in Snapdragon LFY and FLO protein Positive regulator of AF3 and PI gen

eristem identity genes l meristem utant: indeterminate flower within fl (sepal, petal, petal etc) gamous (AG) in Arabidopsis ena (PLE) in Snapdragon otein: putative transcription factor

eristem maintenance genes em: - small, dense, large nuclei - to supply new cells - undifferentiated cells (central) - daughter cells with specific developmental fates (sub

Meristem maintenance genes ant: no meristem (strong allele) Reduced number of meristematic No effect of root meristem ot meristemless, stm -5 mutant: 1-2 leaves then terminate leaf primordia consume central z

Meristem maintenance gen TM protein: Produced throughout developmen Maintain shoot and floral meristem Inhibit differentiation in central zo Activate cell division/proliferation

Floral Initiation Process (FLIP bidopsis structural development - rosette leaves with compact intern - elongated internode with cauline le and lateral inflorescence (bolting - nodes without leaves and flowers

Floral Initiation Process (FLIP ansition from early to late infloresce Loss of indeterminate growth Inhibit inflorescence program Inhibit leaf, lateral shoot developme Initiate specific floral organ Activate perianth development nhibit reproductive organ developm

P genes LFY AP1 AP2 timing of phase transition utant: correct sequence of developm arly bolting arly flowering duced number of inflorescence inter

1/AP2: required in combination rapid and complete transition t: gradual transition from inflo. to flower-like lateral shoot leaf in first whorl reproductive organs in outer whorls etc. n flower development duce FLIP genes, increase gamete ge

rgan Identity s with appropriate identity for their el ses of genes: A, B and C ng individual and in pair C inhibit/antagonize each other o simultaneous functions)

B A 1 C 2 3 4 sepals whorl 1 B petals whorl 2 C stamens whorl 3 carpel and determinacy whorl

model: eloped from floral homeotic mutants f Arabidopsis and Antirrhinum flowers with abnormal organ pattern es identified: MADS-box family transcription factor with conserved d work well in petunia, tomato and ma

A mutant abnormal in whorl abnormal in organ B mutant abnormal in whorl abnormal in organ C mutant abnormal in whorl abnormal in organ

AP1, SQUA Mutant sepal to leaves and no petal Class AP2 Mutant sepals to leaves or carpels petals to stamens Class

3, DEF tant petals to sepals and stamens to car ss , PLE tant stamens to petals and carpels to se ss

ss mutant with different phenotype aried from predicted pattern e floral homeotic genes (MADS bo ot follow ABC model: new E-class ontrol 3 inner whorls and determ model necessary but not sufficient **D-class for ovule identit

-class or Identity mediating fa m genes: MADS box genes Transcription factor abidopsis SEP etunia FBP2 mato TM5 utants: changes in organ identity in 3 inner whorls loss of determinacy

opsis triple mutant (sep1 sep2 sep epals epals epals w mutant flower a FBP2: functional equivalent to SEP mplementation of sep mutant) essential for function of B and C cla

Revised ABC model B Im/E class A and C Other factors sepal petal stamen car

rtet model of floral organ iden action between MADS-domain prote o form DNA binding dimers -class protein form dimer with each or with A-class protein -class protein with E-class protein ary or quaternary complex - and C-class protein with -class and E-class protein

Floral organ identity lled by 4 different combinations of oral homeotic proteins Arabidopsis 1: A-class AP1 homodimer 2: A-class AP1, B-class AP3 and PI, E-c 3: B-class AP3 and PI, C-class AG, E-cla 4: C-class AG, E-class SEP heterodime

Blooming gene to flower nter spring summer early: no pollinating insect late: not enough time to make seed ne: CONSTANS in Arabidopsis ntrol flowering time NSTANS protein helps measure day le

ty of light erceived by 2 light receptors yptochrome 2 responds to blue light hytochrome A responds to red light TANS protein: amount above thresh receptors: activated ght: late afternoon time for flowering undreds of genes involved to build flo

Color and Color pattern color: important for pollination nt perception of color flower – visible to hummingbird -- colorless to bee es in petal color : effect on pollinator attern: differential accumulation of

Color and Color pattern wer color: Accumulation of flavonoids Major pigments: anthocyanins orange, red and purple cuole: site of anthocyanin accumulat ansport as glutathione conjugate

Flower Color Anthocyanin synthesis pathway Biosynthesis enzymes/gene identified

Flower Color anin synthesis pathway lation at transcriptional level t colors: different enzyme activities trate/precursor availability in differe ns: accumulation of intermediates new color

Flower Color Factors on flower perception co-pigmentation vacuolar pH cell shape

Flower Color o-pigmentation anthocyanin and flavonols / flavon shift in absorption spectrum fferential gene expression: different enzyme activities changes in pigment ratio

Flower Color olar pH H increase blueing even loci (ph1-ph7) control pH in pet utation of the ph loci effect on pH in petal extract but not on anthocyanin compositio regulatory genes?

Flower Color ll shape effect on optical properties conical shape: higher light absorpt appear velvet sheen flat shape: faint color

Flower Color l-shape controlling gene: mixta homolog of gene for Myb-domain pr proposed function: regulatory gene molecular mechanism: still not know

Color and Color pattern or pattern cell-specific accumulation of pigmen specified by expression pattern of regulatory genes that control anthocyanin-synthesis genes

Color pattern utant with altered pigment synthesi mutated structural (enzyme) gene mutated regulatory genes wo classes of regulatory genes ident TF with MYB domain TF with bHLH motif

Color pattern get genes to be regulated specific cis (responsive) elements essential for protein-DNA interac resulting in transcription activat species-specific sequence spatial / temporal specific sequence

Color and color pattern ny factors still unknown re information leads to applied rese netic engineered cutflowers with novel color and color pattern

Ornamental crop Improvemen Color Fragrance Nectar Shape Vase life Disease resistance

Transformation (cocultivation with Agrobacterium Rose Chrysanthemum Carnation Tulip Lily Freesia Snapdragon Anthurium Embryogenic callus Leaf Peduncle PetalStem

Molecular breeding ne transformation then Selection ower color Maize dfr to petunia: brick-red petu Petunia mum gerbera rose chs suppression/Antisense technique rious pattern and color white pale pink cream etc.

latory gene for anthocyanin pathwa aize Lc to petunia: red plant napdragon del to gerbera: red leaf and flower scape not in flo life: ethylene t: s-linalool synthase (monoterpene)