Coordinating the morphogenesis-differentiation balance by tweaking the cytokinin-gibberellin equilibrium

Abstract

Morphogenesis and differentiation are important stages in organ development and shape determination. However, how they are balanced and tuned during development is not fully understood. In the compound leaved tomato, an extended morphogenesis phase allows for the initiation of leaflets, resulting in the compound form. Maintaining a prolonged morphogenetic phase in early stages of compound-leaf development in tomato is dependent on delayed activity of several factors that promote differentiation, including the CIN-TCP transcription factor (TF) LA, the MYB TF CLAU and the plant hormone Gibberellin (GA), as well as on the morphogenesis-promoting activity of the plant hormone cytokinin (CK). Here, we investigated the genetic regulation of the morphogenesis-differentiation balance by studying the relationship between LA, CLAU, TKN2, CK and GA. Our genetic and molecular examination suggest that LA is expressed earlier and more broadly than CLAU and determines the developmental context of CLAU activity. Genetic interaction analysis indicates that LA and CLAU likely promote differentiation in parallel genetic pathways. These pathways converge downstream on tuning the balance between CK and GA. Comprehensive transcriptomic analyses support the genetic data and provide insights into the broader molecular basis of differentiation and morphogenesis processes in plants.

Cytokinin-microbiome interactions regulate developmental functions

“…4 C). We therefore next conducted an in depth analysis of leaf development, which follows a predictable and well characterized program in S. lycopersicum M82 [ 26 , 29 ], following treatment with B. megaterium isolate 4C. We found that starting from p3, B. megaterium 4C treatment results in a significant increase in leaf patterning (Fig.…”

“…The KNOXI gene Tkn2 plays important role in promoting leaf morphogenesis by delaying differentiation, preserving the meristematic identity of the leaf margin. The NAM-CUC transcription factor GOBLET determines boundaries within meristematic regions, that are necessary for organ initiation [ 30 , 53 ], while the MYB transcription factor CLAU regulates the exit from the morphogenetic phase of tomato leaf development by affecting the CK / GA balance [ 26 ]. The changes in the expression levels of these genes upon treatment with bacilli isolated from high-CK genotypes (Fig.…”

“…Primer sequences used for the qRT-PCR analyses are detailed in Additional file 1 : Table S1 [ 22 , 30 ]. For developmental gene analysis, we chose genes related to boundary definition, which is important for organ initiation [ 30 , 52 ], meristem maintenance, which is important for increased morphogenesis [ 26 ], and, given the TCSv2 activation results, genes of the CK pathway. Expression of all assayed genes was normalized relative to a geometric mean of the copy number of the three tomato housekeeping genes, ribosomal protein SlRPL8 (Solyc10g006580), Slcyclophilin (Solyc01g111170) and SlEXP (Solyc07g025390).…”

“…Height from the stem base to the SAM, and fresh weight were measured using a ruler and an analytical scale, respectively. For developmental analyses, we chose to examine leaf development, which follows a predictable and well characterized program in S. lycopersicum M82 [ 26 , 29 ], in depth. For this, we selected the B. megaterium isolate 4C, which consistently performed best in growth promotion assays we conducted (Fig.…”

The VIL gene CRAWLING ELEPHANT controls maturation and differentiation in tomato via polycomb silencing

“…The elaboration of compound leaves depends on slow maturation of the developing leaf, which enables an extended organogenesis activity at the leaf margin, during which leaflets are formed [25][26][27][28][29]. Leaflets are formed by differential growth at the leaf margin, where regions of blade growth are separated by intercalary regions of growth inhibition [30].…”