Tuan-Hua David Ho - US grants

Gibberellic acid (GA), a plant hormone, regulates several important physiological and developmental processes such as seed germination, post-germination growth, stem elongation and flower induction. Together with another hormone, abscisic acid (ABA), GA is known to regulate the synthesis and secretion of several enzymes which are responsible for the utilization of nutrients stored in the seed. The enzymes are essential for post-germination growth of many cereal grains. The most abundant of these enzymes is alpha-amylase, which degrades starch. As part of a long term effort to elucidate the mode of action of GA and ABA this research will focus on gene expression in the aleurone layers of germinating barley seeds. Previous research has revealed that hormone-mediated regulation of enzyme expression in the barley-aleurone system is mainly at the level of gene transcription. The proposed research will investigate specific interactions between specific protein factors with regulatory regions (promoters) of hormone-regulated genes in the barley-aleurone system. Goal for this research include: (1) determination of specific DNA sequences in the alpha-amylase promoters that interact with protein factors, (2) investigation of the effect of hormonal treatments on the activity of the protein factors, (3) determination of the importance of promoter sequences inside the aleurone cells and (4) investigation of the activity of these factors in genetic mutants with altered sensitivities to GA and ABA. Results from this research should improve our understanding of the primary action of GA and ABA, thus revealing new insights into the signal transduction pathway governing hormonal regulation of gene expression in plants.

9408900 Ho The plant hormone, gibberellin (GA), exerts regulatory roles in several important physiological and developmental processes such as seed germination and post-germination growth, stem elongation and flower induction. Gibberellin and another hormone, abscisic acid (ABA), are known to regulate the synthesis and secretion of several enzymes which are responsible for the utilization of nutrients stored in cereal grains. The most abundant among these enzymes are the starch-degrading alpha-amylases and the storage protein- degrading proteinases. As the continuation of long term effort in elucidating the mode of action of these two plant hormones, the effect of hormones on the coordinated expression of alpha-amylase and protease genes will be studied in the aleurone layers of germinating barley seeds. Specifically it is planned to: 1) analyze the cis-acting elements in the protease promoter that are responsible for hormonal regulation, 2) investigate how GA and ABA regulate the level/activity of this DNA binding protein, and 3) isolate and characterize cDNA clones for "early" GA-induced genes whose expression has been suggested to be important for later alpha-amylase and proteinase expression. It is hoped that the information obtained in this proposed project will contribute to our understanding of the molecular action of these hormones on gene regulation in plants. ***

Award Abstract - 9876691

This award will support the fabrication of a new kind of metal particle, by lithography and metal deposition, and the testing of these particles in important areas of biological research. These designer particles will be produced and tested for biolistics-mediated genetic transformation of plant and mammalian cells. The particular biological testing studies to be conducted with the designer particles include (1) a comparative study of plant genetic transformation efficiency by biolistics between the gold designer particles and conventional tungsten and gold particles (2) the use of cobalt designer particles for the study of the viscoelastic response of model tissues by the using magnetic tweezers to apply oscillating or static forces to magnetic designer particles embedded in the model tissue, and (3) a comparative study of mammalian cell transformation efficiency by biolistics between conventional gold particles and gold designer particles. These studies will include the delivery of DNA vaccines, green fluorescent protein-myosin fusion proteins, and molecules controlling assembly and disassembly of neuronal processes in the retina, mutant ion channels.

The antagonism between two phytohormones, gibberellins (GA) and abscisic acid (ABA), regulates the transition from seed formation to seed germination as well as several other physiological and developmental processes in plants. This proposed project is designed to investigate the molecular basis of this hormone antagonism in the aleurone cells of barley seeds, where the action of these two hormones can be conveniently monitored by the activity of several marker genes encoding enzymes such as a-amylases, proteases, or a group of unique proteins called late embryogenesis abundant (LEA) proteins. The GA/ABA antagonism has long been recognized as non-competitive in nature, and it has been observed that the action of ABA in this antagonism is sensitive to inhibitors of the gene transcription process. Recent results suggest that an ABA induced regulatory molecule, the protein kinase PKABA1, is a key intermediate in suppressing the GA-regulated gene expression. The objective of this proposed project is to further elucidate the role of PKABA1 in GA/ABA antagonism and to investigate the mechanisms underlying its interactions with other signal transduction components mediating the action of GA and ABA. The specific aims in this project include: 1) to investigate how ABA and GA regulate the synthesis of PKABA1, 2) to determine whether the expression of PKABA1 is mediated by the activity of a lipid-degrading enzyme, phospholipase D (PLD), an early ABA signal transduction component, 3) to "map" the site of action of PKABA1 in relation to other known signaling molecules, 4) to determine the functional domains of the PKABA1 molecule, which are important for its regulatory roles, and 5) to study how the levels and activities of regulatory molecules important for the GA induction of gene expression can be affected by ABA treatment or PKABA1. A multi-discipline approach employing biochemical, genetic, cell and molecular biology techniques will be followed in carrying out this project. It is hoped that this proposed project would not only reveal new insights into the molecular basis of interactions between two important groups of phytohormones, but also the role of a unique protein kinase in plants. Since regulation of seed germination has been an important problem in agriculture, it is conceivable that the information obtained in this project could also lead to potential applications. In addition to the training of one postdoctoral fellow and one graduate student, the participation of several undergraduate students throughout this project is also anticipated.