Periodic Reporting for period 1 - SCALE (Evolution of organ size scaling in plants)
Okres sprawozdawczy: 2022-01-01 do 2023-12-31
The phenomenon of allometric scaling, which maintains consistent size relationships among different organs within a species, is widespread in biology. However, during evolution, morphological scaling relationships among organs can be modified, leading to the emergence of new relationships. Understanding how allometry is maintained and evolves at the molecular level remains a challenge, despite its importance in deciphering how the size of specific organs is controlled. This research aimed to elucidate the molecular mechanisms governing the expression of a general growth regulator and its implications for organ development. The SCALE project sought to identify crucial regulatory sequences that determine the expression of such a gene. Subsequently, it investigated the proteins interacting with these sequences and their influence on the expression pattern of the general growth regulator in different organs. Finally, the project aimed to determine how changes in regulatory sequences can affect gene expression in specific organs. Through this project, we aimed to gain a deeper understanding of the regulatory architecture of general growth regulators and underscore important molecular concepts for manipulating the size of specific organs. SCALE demonstrated that a key general growth regulator is regulated by identical hormonal signals in all organs, thereby ensuring the maintenance of allometry between organs. Additionally, SCALE results strongly suggested that the expression pattern of this gene within developing organs depends on the presence of regulatory proteins that render cells sensitive to hormones, and how identity can modulate the expression of such genes, providing a means to modify allometric scaling among organ size.
To unravel the molecular basis of organ size scaling, SCALE employed a comprehensive approach integrating bioinformatics, molecular genetics, and cellular techniques within the model plant Arabidopsis thaliana. Initially, bioinformatic analyses were conducted to identify Conserved Non-Coding Sequences (CNS) within the regulatory regions of general growth regulators, along with their putative regulating transcription factors. Subsequently, a series of sequence deletion constructs were generated to elucidate the functional relevance of these CNSs in governing the expression of a general growth regulator across various plant organs. These analyses revealed the indispensability of three regulatory sequences, each containing tandem repeats of binding sites for a class of transcription factors known to respond to the plant phytohormone, auxin. Specific deletion of these sites further validated their critical role in conferring expression of the growth regulator. Chromatin Immunoprecipitation experiments, coupled with gene expression studies, elucidated that these sequences are bound by several members of this transcription factor family, operating redundantly to promote the expression of the general growth regulator during early organ development. The study concluded that the expression pattern of this gene is primarily dictated by the ability of cells to sense auxin signal during organ growth. Moreover, bioinformatics analyses suggested that the regulatory sequences of this gene are also bound by organ identity factors, a finding corroborated through Chromatin Immunoprecipitation experiments. The study of this interactions indicated that they contribute to shaping the gene's expression in specific organs by bypassing auxin activation signals. Furthermore, quantitative modification of the gene's sensitivity to the auxin signal appeared to alter levels of the growth regulator at a cellular level, thereby influencing the rate of organ growth. Throughout these studies, the SCALE project also developed novel methodologies to simultaneously quantify gene expression and protein levels at a cellular resolution in intact plant tissues. Part of these results has been disseminated through three publications in high-profile journals, with additional publications currently being prepared. The findings have also been communicated at a global scale at national and international conferences and within the host institution through seminars, collaborations and workshops.
SCALE has significantly advanced our comprehension of the molecular mechanisms underlying organ size regulation and the maintenance of organ dimensions relationship. By shedding light on new concepts and regarding the manipulation of organ size, the project has laid the groundwork for further exploration and exploitation of fine tuning plant architecture to optimize agricultural crops. These insights hold promise for future applications in sustainable agriculture and the development of highly productive agricultural systems. Moreover, the project has pioneered the development of Whole-mount Single Molecule RNA In Situ Hybridization as a method for accurately quantifying mRNA molecules at a cellular resolution across plant tissues. This innovative method, which is simple and compatible with protein quantification, has unlocked a myriad of possibilities for addressing novel questions within the scientific community.
Furthermore, SCALE has facilitated collaborations among researchers at both national and international levels, fostering knowledge exchange and contributing to the training and career development of numerous young scientists. Cutting-edge training in cellular and epigenomics approaches was provided not only at the host institution but also through engagements with several external laboratories.
Furthermore, SCALE has facilitated collaborations among researchers at both national and international levels, fostering knowledge exchange and contributing to the training and career development of numerous young scientists. Cutting-edge training in cellular and epigenomics approaches was provided not only at the host institution but also through engagements with several external laboratories.