Biochemistry ppt

1. Regulation of Defense
Flavonoid Formation in
Legumes
Zeeshan Akram Hanjra
15211506-050
Bs Botany 8th (A)
Plant Biochemistry-II (Bot-402)

2. Introduction
 Many types of compounds effective in defense
in legumes of the Fabaceae, including
glycoproteins, callose, glucanases, chitinases,
peroxidases, and phenolics associated with
the inner cortex of nodules.
 Proanthocyanidins and isoflavans in legumes
such as Lotus and pterocarpans such as
glyceollin and medicarpin in soybean and
alfalfa, respectively, are major flavonoid
defense products.

3. Regulation of defense flavonoid
formation in legumes
 Regulation of flavonoids involved in root
symbioses is controlled both endo- genously
via internal signals and exogenously via
external followed by internal signals.
 Non-phytoalexin types of flavonoids, including
isoflavones, secreted into the rhizosphere as
chemotactic agents or nodD gene activators
necessary for initial nodule formation, are
formed in root epidermal cells controlled by
endogenous regulatory systems.

5. Cont.
 F3H, DFR, isoflavone reductase (IFR), and
vestitone reductase ,RNAs of F3H and DFR are
accumulated at a higher level in nodules than in
roots of alfalfa.Promoter characteristics of CHS
have been studied in both soybean and alfalfa.
 Cis-ele- ments of the promoters of elicitor-
inducible genes of CHS, PAL, and IFR have
been studied in soybean, bean, and alfalfa.

6. Genes and Proteins involving in
the regulation of defense flavonoid
 Only a few regulatory genes involving the
flavonoid pathway in legume roots have been
identified. A and A2 in Pisum sativum regulate
CHS activity. Neither has been cloned.
 A series of regulatory proteins that bind to the
promoter of CHS, however, have been isolated
from Phaseolus vulgaris (bean): SBF-1
(silencer binding factor) and KAP- 1,2 (H-box
binding factors).

7. Conti.
 Plant genes common to both nodular and
arbuscular symbioses have been postulated, but
so far none is known.
 Some genes must be specific to each type of
symbiosis. Genes and proteins of 12 nodulin
genes, expressed in the invasion zone as early
(ENOD) and late (NOD) genes, have been
described in nodules of alfalfa, soybean, and
broad bean.
 Examples are the early nodulin ENOD2, a wall-
localized hydroxyproline-rich glycoprotein of the
nodule cortex implicated in defense and the
limitation of diffusion, and ENOD40, which alters

8. Thank you
!