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.
