Transcriptomics Analysis Reveals a Putative Role for Hormone Signaling and MADS-Box Genes in Mature Chestnut Shoots Rooting Recalcitrance

Abstract

Maturation imposes several changes in plants, which are particularly drastic in the case of trees. In recalcitrant woody species, such as chestnut (Castanea sativa Mill.), one of the major maturation-related shifts is the loss of the ability to form adventitious roots in response to auxin treatment as the plant ages. To analyze the molecular mechanisms underlying this phenomenon, an in vitro model system of two different lines of microshoots derived from the same field-grown tree was established. While juvenile-like shoots root readily when treated with exogenous auxin, microshoots established from the crown of the tree rarely form roots. In the present study, a transcriptomic analysis was developed to compare the gene expression patterns in both types of shoots 24 h after hormone and wounding treatment, matching the induction phase of the process. Our results support the hypothesis that the inability of adult chestnut tissues to respond to the inductive treatment relies in a deep change of gene expression imposed by maturation that results in a significant transcriptome modification. Differences in phytohormone signaling seem to be the main cause for the recalcitrant behavior of mature shoots, with abscisic acid and ethylene negatively influencing the rooting ability of the chestnut plants. We have identified a set of related MADS-box genes whose expression is modified but not suppressed by the inductive treatment in mature shoots, suggesting a putative link of their activity with the rooting-recalcitrant behavior of this material. Overall, distinct maturation-derived auxin sensibility and homeostasis, and the related modifications in the balance with other phytohormones, seem to govern the outcome of the process in each type of shoots.

Ethylene Action Inhibition Improves Adventitious Root Induction in Adult Chestnut Tissues

“…Several players are believed to take part in this connection between AR and recalcitrance, particularly hormones, epigenetic mechanisms and their crosstalk, which may underlie developmental plasticity in plants [ 33 ]. A recent analysis showed that transcriptomic responses to auxin and wounding vary greatly between the two types of microshoots used in the present study [ 20 ]. Among the differences found, mature shoots exhibit an increased response related to ET, including biosynthesis-related genes and ET-responsive transcription factors.…”

“…Every step in the AR process is subject to a dynamic and specific hormone modulation, although auxin is the key hormone in AR [ 18 ]. The decline of the rooting ability after the transition from the juvenile to the mature stage is linked to changes in auxin homeostasis [ 11 , 16 ], modifying the expression of auxin-responsive genes [ 19 , 20 ]. However, other plant hormones are involved in the regulation of AR.…”

“…In chestnut, a transcriptomic analysis revealed that signalling related to different hormones such as abscisic acid or ethylene is upregulated in mature tissues in response to auxin and wounding when compared to juvenile tissues. Among them, ethylene signalling genes were found, which led to the hypothesis that higher concentrations of ET in mature tissues could be one of the causes underlying its recalcitrant behaviour [ 20 ]. ET biosynthesis and signalling pathways have been properly characterised in plants, leading to the development of specific strategies that allow for their modulation.…”

Cloning and functional analysis of ZmMADS42 gene in maize

“… 22 , 23 These roles include hormone response, seed germination, flower development, and overall plant morphogenesis. 24 , 25 Research indicates that the ZmMADS1 gene functions as a regulatory factor for flowering time in plants. When ZmMADS1 is downregulated by RNA interference, maize exhibits delayed flowering, whereas its overexpression results in earlier flowering, establishing it as a flowering activator.…”

Wounding-Related Signaling Is Integrated within the Auxin-Response Framework to Induce Adventitious Rooting in Chestnut

“…Then, a transcriptomics time-series analysis was developed to depict the genetic responses of chestnut to wounding and wounding plus auxin in order to characterize the molecular processes that are triggered by these two stimuli. Particularly, we focused on the early stages after the beginning of the treatments, where specific cells within the base of the stems might be responsive and able to trigger a cellular reprogramming driving the initiation of roots [ 10 , 11 ]. The results obtained suggest that wounding triggers a molecular response that paves the way for the rooting process, but several relevant genes fall short of the expression level needed to induce the formation of the roots.…”