Characterization of Xantha-m involved in chloroplast development in barley (Hordeum vulgare L.)
(2021) MOBN03 20202Degree Projects in Molecular Biology
- Abstract
- Five Xantha-m chlorophyll-deficient mutants which are lethal after the seedling stage have been already discovered in barley (Hordeum vulgare L.) and a candidate gene, SecA1, was recently identified by Bulked segregant analysis (BSA). SecA1 protein participates in the stroma-to-lumen protein transfer across the thylakoid membrane. In this study, the Xantha-m gene was analyzed. Western blotting experiments confirmed that the protein is present in etiolated plants in a wild type and does not increase the amount during photomorphogenesis. Xan-m.73 mutant has a point mutation and produce a protein of approximately the same size as the wild type. Xan-m.3 and xan-m.72 produce truncated proteins and xan-m.48, xan-m.53 do not produce any protein.... (More)
- Five Xantha-m chlorophyll-deficient mutants which are lethal after the seedling stage have been already discovered in barley (Hordeum vulgare L.) and a candidate gene, SecA1, was recently identified by Bulked segregant analysis (BSA). SecA1 protein participates in the stroma-to-lumen protein transfer across the thylakoid membrane. In this study, the Xantha-m gene was analyzed. Western blotting experiments confirmed that the protein is present in etiolated plants in a wild type and does not increase the amount during photomorphogenesis. Xan-m.73 mutant has a point mutation and produce a protein of approximately the same size as the wild type. Xan-m.3 and xan-m.72 produce truncated proteins and xan-m.48, xan-m.53 do not produce any protein. Transmission electron microscopy results show that the chloroplasts in mutants are not well-structured and very different from the wild type. The overall results of this study provide a better understanding of SecA1 function. In the future, this knowledge may help to complete the picture of the chloroplast bioginesis in plants. (Less)
- Popular Abstract
- Controlling protein traffic on chloroplast borders
Chlorophyll is a green pigment crucial in photosynthesis, allowing most plants and algae to use energy from sunlight. The proper function of chlorophyll relies on fully developed organelles of a cell, called chloroplasts. In barley, a protein, involved in chloroplast development, was recently identified by Bulked segregant analysis of five chlorophyll mutants. This protein is SecA1 and it is encoded by Xantha-m gene.
While developing, chloroplast need “resources” to start the production of chlorophyll to use sunlight energy. Some “resources” are luminal proteins, that are transported across thylakoid membrane inside a chloroplast. The membrane can be thought of as a border, and... (More) - Controlling protein traffic on chloroplast borders
Chlorophyll is a green pigment crucial in photosynthesis, allowing most plants and algae to use energy from sunlight. The proper function of chlorophyll relies on fully developed organelles of a cell, called chloroplasts. In barley, a protein, involved in chloroplast development, was recently identified by Bulked segregant analysis of five chlorophyll mutants. This protein is SecA1 and it is encoded by Xantha-m gene.
While developing, chloroplast need “resources” to start the production of chlorophyll to use sunlight energy. Some “resources” are luminal proteins, that are transported across thylakoid membrane inside a chloroplast. The membrane can be thought of as a border, and SecA1 protein is an ATPase – “border patrol agent”, allowing luminal proteins to come through a protein channel. If the “agent” is malfunctioning or absent, the “custom” cannot work properly, and eventually chloroplast will not be fully developed and will not perform photosynthesis. It’s easy to see on the five Xantha-m barley mutants – all of them are deficient in chlorophyll synthesis and thus appear yellow (see the illustration).
DNA sequencing of Xantha-m mutants revealed that the mutants have severe mutations, preventing a proper function of SecA1 protein and causing lethality after seedling stage. Western blot showed that xan-m.3 and xan-m.72 mutants were able to produce truncated variants of the protein, while xan-m.48 and xan-m.53 did not produce any. Xan-m.73 produced a protein of the same size as SecA1, which could remain some function, since this it had the highest relative chlorophyll level of all five mutants.
Western blot protein analysis of seedlings, grown in the dark, suggests that the protein is involved in the early stages of chloroplast development, when the seeds germinate in soil. Since this step is light-independent, it is possible that the protein does not regulate photosynthesis directly, but “prepares the ground” for it by transporting the luminal proteins for chloroplast biosynthesis. Transmission electron microscopy showed a very close view of Xantha-m mutants, where it was clear that the chloroplast could not function due to the abnormal chloroplast structures.
Just like a lock require a key to open it, SecA1 protein is needed to allow necessary proteins through a channel in thylakoid membrane. It may seem like a minor issue in chloroplast development, but if chlorophyll won’t be properly synthesized, the plant won’t perform photosynthesis and eventually die. Thus, understanding of SecA1 role in the chloroplast development and function will allow better understanding of how the cell prepare itself for and function during photosynthesis. In turn, photosynthesis could be seen as one of the features of genetically engineered organisms that will colonize other planets or simple addition to our knowledge about the world.
Master’s Degree Project in Molecular Biology 60 credits 2021
Department of Biology, Lund University
Advisors: Mats Hansson, David Stuart
Molecular Cell Biology Unit (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9055858
- author
- Ivanova, Anastasiia
- supervisor
-
- Mats Hansson LU
- David Stuart LU
- organization
- course
- MOBN03 20202
- year
- 2021
- type
- H2 - Master's Degree (Two Years)
- subject
- language
- English
- id
- 9055858
- date added to LUP
- 2021-06-17 10:49:44
- date last changed
- 2021-06-17 10:49:44
@misc{9055858,
abstract = {{Five Xantha-m chlorophyll-deficient mutants which are lethal after the seedling stage have been already discovered in barley (Hordeum vulgare L.) and a candidate gene, SecA1, was recently identified by Bulked segregant analysis (BSA). SecA1 protein participates in the stroma-to-lumen protein transfer across the thylakoid membrane. In this study, the Xantha-m gene was analyzed. Western blotting experiments confirmed that the protein is present in etiolated plants in a wild type and does not increase the amount during photomorphogenesis. Xan-m.73 mutant has a point mutation and produce a protein of approximately the same size as the wild type. Xan-m.3 and xan-m.72 produce truncated proteins and xan-m.48, xan-m.53 do not produce any protein. Transmission electron microscopy results show that the chloroplasts in mutants are not well-structured and very different from the wild type. The overall results of this study provide a better understanding of SecA1 function. In the future, this knowledge may help to complete the picture of the chloroplast bioginesis in plants.}},
author = {{Ivanova, Anastasiia}},
language = {{eng}},
note = {{Student Paper}},
title = {{Characterization of Xantha-m involved in chloroplast development in barley (Hordeum vulgare L.)}},
year = {{2021}},
}