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The role of kinesins in male-derived fertility in Arabidopsis thaliana

Mendes, Isabella Natalia
http://orcid.org/0000-0001-6515-2150
http://rave.ohiolink.edu/etdc/view?acc_num=osu1721053950787083

Abstract Details

2024, Doctor of Philosophy, Ohio State University, Molecular Genetics.
Plant reproduction has been of interest to humans since the advent of agriculture over 10,000 years ago in ancient Mesopotamia. Knowing when and how plants reproduced allowed humans to cultivate them and gradually over time increase crop yields through unguided selective breeding. In our present day, the cycles of plant reproduction are still of paramount importance. The reproductive stage of plants is often the most susceptible to environmental fluctuations. Thus, as our climate changes, it is becoming increasingly important to understand the core molecular mechanisms of plant reproduction. For genetically engineered plants to withstand the effects of climate change, we must first understand the molecular mechanisms of plant reproduction. Unlike in animals, where each individual sperm cell is self-motile via the use of a flagella, plant sperm cells are not self-motile. They possess no flagella or means of independent motion. Instead, the sperm of plants relies on the specialized pollen tube structure to deliver plant sperm from the pollen grain to the ovule for fertilization. The pollen tube is a single cell that grows from a pollen grain in a tip-growing manner. It grows down into the female tissue of the flower. Within each pollen tube are two sperm cells. These two sperm cells connect to the vegetative nucleus of the pollen tube itself to form a unit collectively called the male germ unit. This unit traffics together through the cytoplasm of the pollen tube as it grows. The mechanism of this motion is not understood. For over 30 years, it has been proposed that this motion is achieved by motor proteins trafficking the male germ unit along the cytoskeleton of the pollen tube. However, the underlying molecular mechanisms involved in this process have remained obscure. In this work, I investigate the 61 kinesins present in the model organism Arabidopsis thaliana to identify motor proteins that play a role in the trafficking of the male germ unit and in male-derived fertility more broadly. A bioinformatic screen was performed on Arabidopsis kinesins. This screen was designed to find kinesins who had a high relative expression in pollen as opposed to their expression in other cells. Data from sixty different tissues or cell types was compiled from the literature and the expression level for each was noted. This data allowed me to determine which of the 61 Arabidopsis kinesins were expressed at relative high levels in pollen. Of the 61 Arabidopsis kinesins, I identified 17 that I classified as “pollen-expressed kinesins” (PEKs), indicating their high relative expression in pollen. For each of these 17 kinesins, T-DNA insertional mutant lines were created and utilized to perform seed set experiments. The number of seeds per silique in each mutant line, as well as the distribution of seeds within the silique, and the length of the silique were recorded. This allowed me to identify several kinesins that are necessary for full Arabidopsis seed set. Of the 17 pollen-expressed kinesins identified, seven had statistically significant reductions in the number of seeds per silique. Loss of PEK12, PEK13, PEK8, and PEK4 resulted in mild or moderate reductions, while loss of PEK14, PEK9, and PEK3 resulted in severe reductions. These three more severe seed set reductions were investigated in their own chapters. PEK14 was investigated in Chapter 3 and PEK3 and PEK9 were investigated in Chapter 4. PEK14 is a KIF4 subfamily member of the kinesin-4 family of kinesins. It is one of only three kinesin-4s in Arabidopsis and is the only pollen-expressed kinesin-4. Loss of this kinesin results in a severe 50% or greater loss in seed. Examination of pek14 has resulted in me identifying several defects with the knockout line. pek14 pollen grains have a reduced pollen viability, grow at a slower rate, have a decreased ability to turn, and display aberrant male germ unit organization. Together, each of these defects can individually contribute towards the seed set reduction observed in pek14. PEK3 and PEK9 are KatD subfamily members of the kinesin-14B family. They contain calponin homology domains, which have been shown in other proteins to function in crosstalk, allowing binding to actin and regulation of actin-microtubule interaction. The seed set defects observed in pek3 and pek9 were not as severe as those observed in pek14. However, the seed set defects of pek3 and pek9 were quite substantial, at about 30%. It was determined that this loss of seed was derived from defects in both male and female tissue of pek3-1. This contrasted it from pek14, which was only a male-derived defect. Analysis of pek3 and pek9 pollen found no reduction in the number of viable pollen grains. More research is needed to determine the function of PEK3 and PEK9 in Arabidopsis reproduction. Together, the data presented herein represent a step forward in understanding the underlying molecular mechanisms of plant reproduction. While much work is still needed to uncover the specific mechanisms on sperm trafficking in the pollen tube, this research represents an initial push to identify specific kinesin motor proteins involved in that process.
Iris Meier (Advisor)
Anna Dobritsa (Committee Member)
Adriana Dawes (Committee Member)
Patrice Hamel (Committee Member)
189 p.
Cellular Biology
arabidopsis; arabidopsis thaliana; male germ unit; mgu; kinesin; trafficking; pollen tube; seed set

Recommended Citations

Citations

  • Mendes, I. N. (2024). The role of kinesins in male-derived fertility in Arabidopsis thaliana [Doctoral dissertation, Ohio State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=osu1721053950787083

    APA Style (7th edition)

  • Mendes, Isabella. The role of kinesins in male-derived fertility in Arabidopsis thaliana. 2024. Ohio State University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=osu1721053950787083.

    MLA Style (8th edition)

  • Mendes, Isabella. "The role of kinesins in male-derived fertility in Arabidopsis thaliana." Doctoral dissertation, Ohio State University, 2024. http://rave.ohiolink.edu/etdc/view?acc_num=osu1721053950787083

    Chicago Manual of Style (17th edition)

osu1721053950787083
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This open access ETD is published by The Ohio State University and OhioLINK.