TY  - GEN
A1  - Luzzietti, Laura
KW  - Open chromatin
secondary growth
Vasculature
AV  - restricted
Y1  - 2025///
CY  - Heidelberg
N2  - ABSTRACT
Continuous growth over their lifetime is one of the plants' striking capacities, which include also the ability to regenerate lost or damaged tissues. In contrast to animals that develop all tissues and organs during embryogenesis, plants have the ability to form continuously new tissues after embryogenesis. Specific undifferentiated cell niches called meristems enable these capabilities of uninterrupted growth and probably evolved in parallel to the sessile lifestyle of plants. Meristems are located in several spots along the plant body.he main meristems forming the basic structure are the apical meristems. Such meristems provide longitudinal growth, supporting the plant's vertical growth and sustaining the newly formed tissues. Members of some species can expand their girth by radially growth due to lateral or secondary meristems, which provide the secondary
growth. Among these secondary meristems is the vascular cambium, a thin layer of undifferentiated cells that feed, in opposing directions, the formation of secondary vascular tissues. Cambium activity is of essential importance on earth. With its special features, the cambium also presents an interesting possibility to study developmental aspects in plants. One great advantage of studying such a tissue is rooted in the fact, that the cambium is located just in
between the different cell types that its division activity produces, the xylem and phloem. Thus, in comparison to other stem cell niches, image tracing and comparable techniques can more easily delineate the development and the cell-fate decision in a spatio-temporal manner. Nevertheless,
the mechanisms that drive differentiation of the cambium are not yet fully understood. While in the last years much effort has been put into a better understanding of the cambium transcriptomic profile, in this study I investigated the cambium from an epigenetic point of view.
In particular, I analyzed the chromatin profile in cambium cells as well as in xylem and phloem precursors. By using fluorescent reporter proteins transcribed under the control of tissue-specific promoters, I sorted and specifically collected nuclei from different cell populations and analyzed the chromatin landscape using the FANS ATAC-seq technique. In this context, I optimized protocols known from animal studies and increased the quality of the output in comparison to previously used procedures. I thus obtained and analyzed the chromatin landscape during the secondary vascular tissue development and found minimal differences among the differentiating tissues. Due to the power of this tool, I decided to focus specifically on phloem development. To this end, I generated and used a fluorescent marker expressed under the promoter of SUPPRESSOR OF MAX2 1-LIKE 5 (SMXL5), whose activity is an important hallmark of phloem
development. To increase the power of my differential analysis, I also used phloem-deficient mutants, such as smxl5, smxl4smxl5 and smxl5obe3 expressing the same fluorescent marker protein. Whereas SMXL5 and SMXL4, the closest homologue of SMXL5, are both specifically expressed
throughout phloem development, OBE3 is a ubiquitously expressed gene also involved in driving phloem development. OBE3 encodes a PHD finger protein potentially binding to chromatin. Recently, it has been shown that SMXL5 and OB3 interact and colocalize into the nucleus. Having analyzed the phloem-specific chromatin profile of the double mutants smxl5obe3 , I thus investigated the OBE3 properties and tested its capacity to bind chromatin in-vitro. This allows us to understand if there is a direct interaction with the histone tails and if binding is taking place. Although the results of the histone binding remained yet unclear, many indications of in-silico analysis point to a function of OBE3 as scaffold protein within nuclear bodies.
TI  - Xylem? Phloem? Cambium? How the chromatin landscape shapes the
development of the vasculature in Arabidopsis thaliana
ID  - heidok35456
UR  - https://archiv.ub.uni-heidelberg.de/volltextserver/35456/
ER  -