This comprehensive presentation explores the intricate genetic mechanisms controlling seed development and maturation. The content covers key stages from embryogenesis through maturation, detailing crucial molecular processes and regulatory networks. Special focus is given to important genes and transcription factors like WOX, LEC, and ABI families, along with hormone signaling pathways involving ABA and GA. The presentation explains critical processes including zygote polarization, tissue differentiation, meristem specification, and the establishment of dormancy. Supported by recent research findings and illustrations, this resource provides valuable insights into the molecular basis of seed development. Perfect for graduate students studying about seed development and maturation.

1. "Gene Expression during seed development and maturation"
P. JAYASANKARAN
Ph.D. Scholar

2.  Seed development and maturation are critical processes in the plant life cycle, ensuring the production of
viable seeds for propagation.
 Seeds undergo embryo development, accumulation of storage reserves, and acquisition of desiccation
tolerance.
 Understanding the gene expression patterns and regulatory mechanisms during these stages is important for
improving seed quality, yield, and agronomic traits.
Introduction

3. Embryogenesis
Seed filling or maturation drying
Desiccation tolerance and dormancy
Stages of Seed Development and Maturation

4. There are two main phases,
1. Morphogenesis - stage of plant body establishment.
2. Maturation - Acquisition of dormancy and germination.
Main stages of morphogenesis
1. Zygote polarity and asymmetric division.
2. Differentiation of tissues.
3. Specification of root and shoot apical meristems ( RAM and SAM).
4. Establishment of cotyledon.
Embryogenesis

5.  Mature egg cell is polarized.
 After fertilization, zygote undergoes asymmetric division.
Regulation of polarization and asymmetric division:
 YDA/MPK cascades involved in polarization & Asymmetric division (zygote elongation and basal cell
lineage development).
 Activated by sperm SSP mRNA.
 WOX2, WOX8, WOX9 – Transcriptional factors involved.
 WOX 2 – In apical cell regulates shoot.
 WOX8 & WOX9 – In basal cell regulates suspensor.
1. Zygote polarity, asymmetric division and its regulation

6. Sangho Jeong et al., 2016
Zhe Wang et al., 2020

7. Periclinal division at octant stages forms dermatogen (16 celled) – Mediated by WOX2 gene.
Outer protoderm layer forms epidermis – Regulated by DEK1 gene.
Globular Stage Tissue Differentiation – Specifications of tissues begins.
Conducting tissues originate from 4 central domain cells (future primary root) via asymmetric
division – Mediated by POL/PLL1.
2. Differentiation of tissues

8.  Root specified from central domain & Shoot specified from apical domain.
 HD-ZIP III expressed in apical domain (SAM).
 PLT (PLETHORA ) genes expressed in central domain (RAM).
 PLT and HD-ZIP III antagonistically determine shoot vs root identity.
 In tpl-1 mutant, PLTs mis-express at both poles.
Ran Tian et al., 2020
3. Specification of root and shoot apical meristems ( RAM and SAM)

9. R. Smith et al., 2010
Nature 464, 423–426 (2010)

10. Occurs during globular to heart stage transition.
Auxin signalling important – mediated by PIN 1 auxin transporters.
Defects in PIN1 can lead to one cotyledon instead of two.
CUP-SHAPED COTYLEDON (CUC 1 & CUC 2) establishes borders between cotyledons and
shoot apical meristem.
CUC defects leads to unequal cotyledon size within a seed.
4. Establishment of cotyledon
Jiayang Li et al., 2017

11. CUC mutants
Tomotsugu Koyama et al., 2017
Plant Physiology 175(2)

12. The Biochemical Journal Tian et al., 2020

14.  ABA induces dormancy, desiccation tolerance.
 LEC 1, LEC 3, FUS 3 are key regulators of seed maturation (Expressed during morphogenesis and maturation
phases).
LEC 1 Functions:
 LEC 1 – Confers desiccation tolerance (Loss causes desiccation sensitivity)
 Balances ABA and auxin levels.
 Stimulates ABA synthesis.
 LEC 2 & FUS 3 – Regulates food reserves accumulation.
Maturation (Acquisition of dormancy and germination)

15. Akiko Kozaki et al., 2022
International Journal of Molecular Sciences
LAFL network genes (includes LEC1, LEC2, ABI3 and FUS3)

16. Jingpu Song et al., 2021
Nat. Commun. 12, 3963 (2021)

17.  LEAFY COTYLEDON (LEC genes) & ABSCISIC ACID INSENSITIVE (ABI) genes: storage reserve synthesis.
(Mutations impair accumulation of storage proteins, lipids, and LEA proteins).
 WRINKLED1 (WRI1): Activates fatty acid biosynthesis genes, impacts seed oil content (WRI 1 mutants have
wrinkled seeds with reduced oil content).
 OPAQUE 2 (O2) : Controls zein (storage protein) accumulation in maize endosperm. (o2 mutants reduced
zein accumulation but increased lysine content).
 Sucrose transporter (SUT) genes: Facilitate sucrose loading into phloem for seed transport.
 SWEET genes: Regulate sucrose unloading from phloem into seeds. (Defects reduce seed filling and
accumulation of reserves).
Storage reserves accumulation

18. SUT & SWEET genes
Mizuno et al., 2016
Biotechnol Biofuels

19.  Images of mature seeds of the null
transgenic (Col-2), mutant (wri1-1), and
wri1-1 expressing LuWRI1a.
WRINKLED1 improves the weight and oil content in seeds of flax (Linum usitatissimum L.)
Front. Plant Sci. - Plant Biotechnology Wenjuan Li et al., 2022

20. Key hormone for induction &
maintenance of dormancy.
NCED gene family encodes enzymes
for ABA biosynthesis.
SnRK2s – Core ABA signalling
component for dormancy induction.
Tuan et al., 2018
Induction of dormancy
Front. Plant Sci. - Plant Physiology
ABA Expression

21. Faiza Ali et al., 2022
Journal of Advanced Research

22. GA Expression
GA20ox, GA3ox – increase bioactive GA
synthesis.
GA2ox: Encodes enzyme inactivating GAs,
higher expression enhances seed
dormancy.
Tuan et al., 2018
Front. Plant Sci. - Plant Physiology

23. Signals and genes Genes involved Roles References
Temperature and
light
AtGA3OX1, AtGA2OX2 PHYA,
PHYB, PHYE
Germination induction
Germination induction
Yamauchi et al. 2004 Heschel et
al. 2008
Phytochrome
related
PHYA PIL5/PIF1
Germination suppression Germination
induction through phyto- chrome-
mediated degradation of PIL5
Heschel et al. 2008; Footitt et al. 2013
Oh et al. 2006
Circadian clock LHY, CCA1, GI, TOC/PRR1, ZTL Dormancy induction and release
Penfield and King 2009; Penfield and
Hall 2009
ABA
ABA1, NCEDs, ABA2/GIN1/SDR1
ABI3, ABI5
FUS3, LEC1, LEC2
ABA biosynthesis
Seed maturation and dormancy induction
Embryo growth arrest, seed maturation, dor-
mancy induction, storage protein expression
Nambara and Marion-Poll 2003 Parcy et
al. 1994; Lopez-Molina et al. 2002;
Holdsworth et al. 2008
Raz et al. 2001; Kagaya et al. 2005; To et
al. 2006
GA
SPT, PIL5, CTS
GA3OX, CYP707A2, MFT
After-ripening process, inhibition of GA
biosynthesis genes (GA3OX1 and GA3OX2)
Seed germination
Russell et al. 2000; Penfield et al. 2005;
Carrera et al. 2007
Kushiro et al. 2004; Yamauchi et al.
2004; Xi et al. 2010
MADS domain
genes FLC, FT, SOC1, AP1 Seed maturation and germination Chiang et al. 2009
Epigenetic
regulation
HUB1, HUB2 &
DOG1
Dormancy induction Liu et al. 2007, 2011 Liu et al.
2011
Faiza Ali et al., 2022
Journal of Advanced Research

24. Seed development and maturation are complex processes involving coordinated gene
expression patterns and regulatory mechanisms.
Elucidating the roles of key genes, transcription factors, and signaling pathways is
crucial for understanding and manipulating seed development and traits.
Conclusion

25. "If agriculture fails, everything else will fail"
Thank You!!!