roles of micrornas in plant abiotic stress, development and viral infection

155 Pages·2017·3.76 MB·English

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University of Kentucky Doctoral Dissertations Graduate School
2008
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University of Kentucky, [email protected]
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Mendu, Venugopal, "ROLES OF MICRORNAS IN PLANT ABIOTIC STRESS, DEVELOPMENT AND VIRAL
INFECTION" (2008). University of Kentucky Doctoral Dissertations. 663.
https://uknowledge.uky.edu/gradschool_diss/663
This Dissertation is brought to you for free and open access by the Graduate School at UKnowledge. It has been
accepted for inclusion in University of Kentucky Doctoral Dissertations by an authorized administrator of
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ABSTRACT OF DISSERTATION

Venugopal Mendu

The Graduate School

University of Kentucky

2008
ROLES OF MICRORNAS IN PLANT ABIOTIC STRESS, DEVELOPMENT AND
VIRAL INFECTION

ABSTRACT OF DISSERTATION

A dissertation submitted in partial fulfillment of the
requirements for the degree of Doctor of Philosophy
in the College of Agriculture at the University of Kentucky

By

Venugopal Mendu
Lexington, Kentucky

Director: Dr. Guiliang Tang, Assistant Professor
Co-director: Dr. Arthur G. Hunt, Professor
Department of Plant and Soil Sciences
Lexington, Kentucky
2008

Copyright © Venugopal Mendu 2008
ABSTRACT OF DISSERTATION

ROLES OF MICRORNAS IN PLANT ABIOTIC STRESS, DEVELOPMENT AND
VIRAL INFECTION

Plant microRNAs play important roles in plant growth and development. Here we
investigated the roles of miRNAs in the plant abiotic stress, development and viral
infection. MicroRNA membrane array analysis using five different abiotic stress
treatments resulted in the identification of 8 novel stress inducible miRNA-families.
Functional studies on novel stress inducible miR168 revealed its functional relation with
abiotic stress. Over expression of miR168 in Arabidopsis showed upregulation of four
stress related miRNAs (miR163, miR167, miR398 and miR408). Analysis of 9
independent transgenic lines showed induction of miR398, an oxidative stress responsive
miRNA with a corresponding down regulation of its target genes. Heavy metal oxidative
stress tolerance bioassays confirmed the susceptibility of transgenics compared to the
wild types indicating the fact that the miR168 is indirectly involved in plant abiotic stress
by inducing other stress responsive miRNAs.
MicroRNAs are highly conserved across the plant kingdom. A miRNA atlas was drafted
for different tomato organs and fruit stages using the known miRNA sequences from
different plants species. A large variation in both number and level of miRNA expression
pattern was observed among different organs as well as among fruit stages. In the present
investigation, we have found a window of expression for different miRNAs during the
fruit development. A gradual decrease in the expression levels of miR160h, miR167a and
miR399d and a gradual increase in miR164a have been noticed towards the fruit
maturation while miR398b showed dual peaks during fruit development indicating a
potential role of various miRNAs in fruit development and maturation.
Sonchus yellow net virus (SYNV) infected Nicotinana benthamiana leaves showed
severe disease symptoms at two weeks post infection (WPI) and gradually recovered
from the SYNV infection after 4-5 WPI correlating with the overall miRNA levels. The
miRNA array and northern analysis showed an overall reduction of miRNA biogenesis
during 2WPI followed by restoration to normal levels supporting the idea that the SYNV
indeed interfered with the host miRNA levels which caused the symptoms and recovery
phenotypes. Overall studies on plant abiotic stress, development and viral infection
showed important roles of miRNAs in different aspects of plant life.

Key words: MicroRNA, plant abiotic stress, plant development, virus, post-
transcriptional gene silencing
Venugopal Mendu
October, 2008
ROLES OF MICRORNAS IN PLANT ABIOTIC STRESS, DEVELOPMENT AND
VIRAL INFECTION

By
Venugopal Mendu

Dr. Guiliang Tang
Director of Dissertation

Dr. Arthur G. Hunt
Co-Director of Dissertation

Arthur G. Hunt
Director of Graduate Studies
October, 2008
DISSERTATION

Venugopal Mendu

The Graduate School

University of Kentucky

2008
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Unpublished dissertations submitted for the Doctor’s degree and deposited in the
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ROLES OF MICRORNAS IN PLANT ABIOTIC STRESS, DEVELOPMENT AND
VIRAL INFECTION

DISSERTATION

A dissertation submitted in partial fulfillment of the
requirements for the degree of Doctor of Philosophy
in the College of Agriculture at the University of Kentucky

By

Venugopal Mendu
Lexington, Kentucky

Director: Dr. Guiliang Tang, Assistant Professor
Co-director: Dr. Arthur G. Hunt, Professor
Department of Plant and Soil Sciences
Lexington, Kentucky
2008

Copyright © Venugopal Mendu 2008
ACKNOWLEDGEMENTS

This dissertation work was carried out under the guidance of my major supervisor Dr.
Guiliang Tang and co-supervisor Dr. Arthur G. Hunt, who have been of great help in my
research and thesis writing. I would like to thank my committee members, Dr. Ling Yuan
and Dr. Peter D. Nagy for their valuable suggestions and guidance in shaping my thesis
objectives. Once again I thank all my committee members for spending their valuable
time and sharing ideas during committee meetings. Particularly the discussions during
committee meetings enlightened me to think about my research in a global perspective. I
would acknowledge all my teachers at school, colleges and Universities, who taught me
and motivated me in science without which, I would not have been accomplished my
academic and research career.

I would like to extend my heartfelt gratitude to faculty, Chair (Dr. Michael Barrett), DGS
(Dr. Arthur G. Hunt) and staff of the Department of Plant and soil sciences for their
encouragement and support during my graduate study at the University of Kentucky. I am
grateful to the Jeffrey fellowship for their support for one year and also the Department
of Plant and Soil Sciences for their financial support during my graduate career. I also
thank faculty and staff of KTRDC for their cooperation and excellent facilities.

Constant support and encouragement given by my mother Vijaya, father, Chandramouli,
brother Ravikumar and sisters Sri Latha and Jyothy, made me travel miles away from
home to pursue my higher studies at the University of Kentucky. Also I really appreciate
the support of my wife Lavanya, who was with me in every moment and helped me to
accomplish this feat. Particularly, her help in thesis and seminar preparation is invaluable.
I would like to thank my dearest friend, Prathap Reddy and his family for their incredible
moral support. I would also like to thank my close friends here in Lexington, and in India
who made my living better by personal and emotional support. Finally, I express my
sincere thanks to all who helped me during my research work and thesis preparation.

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