Transcriptome changes of tomato internode elongation induced by far-red light 3 59 gibberellin, and brassinosteroids facilitate wood formation in stem and stem elongation in tomato (Lee et al., 2019; Schrager-Lavelle et al., 2019; Thompson & Jacobs, 1966). Auxin has also been reported to function in SAS stem elongation in older tomatoes (24 dag (days after germination)) (Cagnola et al., 2012; Courbier et al., 2020), but how auxin regulates younger plant signaling and the detailed regulatory pathway have not been fully resolved. In this chapter, we aim to contribute to stem-specific studies of developmental changes in the SAS and identify transcriptome patterns during supplemental FRregulated shade avoidance in tomato. Figure 3.2. Stem growth on cellular level is regulated by hormones. This graph summarizes findings from arabidopsis. Genes colored in light green are some very well studied receptors or pathway genes that show a function in cell activities in stem growth. Adapted from (Greulach and Haesloop, 1958; Anastasiou et al., 2007; Dello Ioio et al., 2008; Perrot-Rechenmann, 2010; Oh et al., 2020). Stem elongation and radial expansion have been studied for a century, but it still remains unresolved how each of the cell types exactly functions in both radial and longitudinal stem expansion. The interfascicular cambium (in red in Figure 1.5) in the vasculature can produce new vascular cells (Aichinger et al., 2012), but we also observed increased pith numbers in Chapter 2. Kraus in the 19th century raised the argument about the inner tissues, especially the pith, as the driving force for stem elongation, while the outer cell layers determine the rate of elongation by enforcing a mechanical constraint (Kraus, 1867; Kraus, 1869). Kutschera proposed the idea that the inner tissues (pith especially) provide the driving force by changing the turgor pressure, whereas the peripheral cell type(s) control the speed of stem elongation (Kutschera, 1992). This idea was further confirmed by Savaldi-Goldstein et al. by constructing epidermis-specific stabilized mutant protein of IAA17 in Arabidopsis (Savaldi-Goldstein et al., 2007). Concordant with this hypothesis, pith cell elongation was observed in SAS in bean (Phaseolus
RkJQdWJsaXNoZXIy MTk4NDMw