Cotton and Maize Primary Root Growth Responses to Water
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COTTON AND MAIZE PRIMARY ROOT GROWTH RESPONSES TO WATER DEFICIT: COMPARATIVE PHYSIOLOGICAL AND METABOLIC ANALYSIS _______________________________________ A Dissertation presented to the Faculty of the Graduate School at the University of Missouri-Columbia _______________________________________________________ In Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy _____________________________________________________ by JIAN KANG Dr. Robert E. Sharp and Dr. Melvin J. Oliver, Dissertation Co-supervisors JULY 2019 The undersigned, appointed by the dean of the Graduate School, have examined the dissertation entitled COTTON AND MAIZE PRIMARY ROOT GROWTH RESPONSES TO WATER DEFICIT: COMPARATIVE PHYSIOLOGICAL AND METABOLIC ANALYSIS presented by Jian Kang, a candidate for the degree of Doctor of Philosophy, Plant Insect and Microbial Sciences, and hereby certify that, in their opinion, it is worthy of acceptance. Professor Robert E. Sharp Professor Melvin J. Oliver Professor Felix Fritschi Professor Abraham J. Koo ACKNOWLEDGMENTS First and foremost, I need to give my most appreciation to my advisors, Dr. Robert Sharp and Dr. Melvin Oliver. I thank them for providing an excellent environment for research and helping me develop my abilities as an independent-thinking researcher. They were generous with their time while discussing experiments, data interpretation and manuscripts. Besides the science, they were also paying much attention on my emotion. Every time when I’m facing difficulties and feel down, they would sense my feeling and encourage me. They are the first advisors or teachers I ever meet who put themselves in an equal position when talking with me. They always tell me about their difficulties and tough experiences in their student years, letting me know that PhD years are both the toughest and the most substantial time in my life and I should dedicate myself to achieve my goals as a real scientist in the future. Their guidance and encouragement were indispensable for my completion of my Ph.D. program. I greatly appreciate my committee members, Drs. Felix Fritschi and Abraham Koo for their valuable suggestions and guidance. I particularly thank Dr. Fritschi for his expertise on plant nutrient and soil properties which helped me conquer problems I was facing when dealing with the field condition experiments. Thanks are also due to Dr. Koo for his invaluable input to the metabolism contents of my study with his expertise. I highly appreciate the training and technical advice provided by Dr. John Boyer and his warm-hearted instructions in the water potential aspect in my study. As a pioneer of modern plant physiology, Dr. Boyer is so humble who gave a model of a real scientist. I ii am also grateful to Drs. Jim Schoelz and Jeanne Mihail for instilling confidence in me to continue my graduate program and helping me with my writing. I really appreciate the current and previous members in the Sharp and Oliver labs. I thank Drs. Elizabeth Hoyos-Miernyk and Priyamvada Voothuluru with my genuine appreciations for their selfless assistance and counsel to my experiments and writing. I am grateful to Drs. Tyler Dowd, Laura Greeley, Rachel Mertz, Kara Riggs, Anderson Silva and Dante Smith as well as Nick Baert, Cheyenne Becker, Jim Elder, Kate Guill, Shannon King, Tyler McCubbin, Paul Sathi and Hallie Thompson for being wonderful collaborators and colleagues. I appreciate Cotton Incorporated for funding my project and thank the Division of Plant Sciences, Interdisciplinary Plant Group, College of Agriculture, Food and Natural Resources and Graduate School for supporting my graduate program. I would like to thank the faculty, staff and fellow graduate students of the Division of Plant Sciences and Interdisciplinary Plant Group for providing a vibrant research and mentoring environment. I also thank Metabolon for the precise processing and analysis of my metabolomics data. I would like to specially mention my friends, Dr. Yutian Feng, Yunshu Fan, Chen Wang, Yao Wang, Jinpeng Wang and Yiyun Xu for their friendship, understanding, hearing and supporting during this long period of my PhD years. Finally, I would give the sincerest appreciations to my family. As a successful scientist, my father, Shaozhong Kang, is always teaching me how be a scientist and a person of iii integrity. Despite his extremely busy schedules, he spent several summer and winter break times to visit me. Even not in the same research area, he is always giving me suggestions and information about plant science studies in China. My mother, Mei Zhu, supports me with her delicate thoughts on my feelings. Her meticulous care for me over these years helped me get over many tough times when facing difficulties in science and daily life. I also want to give my thanks to my grandparents and other family members. Their presence is the fountain of constant inspiration and happiness in my life. iv TABLE OF CONTENTS ACKNOWLEDGEMENTS ······································································· ⅱ LIST OF TABLES ·················································································· ⅺ LIST OF FIGURES ·············································································· ⅺⅱ LIST OF ABBREVIATIONS ································································· ⅹⅴⅱ ABSTRACT ························································································· ⅹⅹ CHAPTER 1. LITERATURE REVIEW ······································································ 1 Introduction ·························································································· 2 Root responses to water deficit··································································· 5 Reactive oxygen species and anti-oxidative mechanisms in plants exposed to water- deficit stress ························································································· 10 Transcriptomics and metabolomics approaches to study plant responses to water deficits ································································································ 13 Cotton responses to water deficit ······························································· 16 The role of sulfur metabolism in plants under water-deficit stress ····················· 21 Justification ························································································· 24 Objectives ···························································································· 25 v 2. ESTABLISHMENT OF A SEEDLING SYSTEM FOR COTTON PRIMARY ROOT GROWTH STUDIES ···································································· 26 Introduction ························································································· 27 Materials and Methods ··········································································· 29 Growth media Cotton genotypes for selection Plant growth conditions Measurement of primary root length and calculation of elongation rate Modification of the seedling system Results ································································································ 31 First trial for genotype selection System modification Second trail of genotype selection Discussion ···························································································· 46 3. KINEMATIC ANALYSIS OF THE COTTON PRIMARY ROOT GROWTH ZONE UNDER WATER DEFICIT CONDITIONS ······································· 49 Introduction ························································································· 50 Materials and Methods ··········································································· 52 Plant growth conditions Harvest of samples for kinematic analysis vi Cell length measurements Kinematic analyses Results ································································································ 55 Cell length profile in different treatments Spatial patterns of cell elongation rate Discussion ···························································································· 62 4. COMPARISON OF WATER POTENTIALS IN MAIZE AND COTTON PRIMARY ROOT GROWTH ZONES UNDER WATER DEFICIT CONDITIONS ······················································································ 64 Introduction ························································································· 65 Materials and Methods ··········································································· 66 Growth condition Primary root growth zone water potential measurement Statistical analysis Results and Discussion ············································································ 67 Conclusion ··························································································· 73 5. COMPARATIVE METABOLITE STUDIES OF PRIMARY ROOT RESPONSES TO WATER DEFICIT IN MAIZE AND COTTON ···················· 74 Introduction ························································································· 75 Materials and Methods ··········································································· 78 vii Collection of tissue samples Metabolomics profiling platform Ultrahigh performance liquid chromatography-tandem mass spectrometry (UPLC- MS/MS) Gas chromatography-mass spectrometry (GC-MS) Metabolite identification and quality control Tissue sample collection for glutathione and hydrogen peroxide measurements Glutathione enzymatic assay H2O2 measurement Statistical analyses Results ································································································