Gibberellin Promotes Shoot Branching in the Perennial Woody PlantJatropha curcas

Abstract

Strigolactone (SL), auxin and cytokinin (CK) interact to regulate shoot branching. CK has long been considered to be the only key phytohormone to promote lateral bud outgrowth. Here we report that gibberellin also acts as a positive regulator in the control of shoot branching in the woody plant Jatropha curcas. We show that gibberellin and CK synergistically promote lateral bud outgrowth, and that both hormones influence the expression of putative branching regulators, J. curcas BRANCHED1 and BRANCHED2, which are key transcription factors maintaining bud dormancy. Moreover, treatment with paclobutrazol, an inhibitor of de novo gibberellin biosynthesis, significantly reduced the promotion of bud outgrowth by CK, suggesting that gibberellin is required for CK-mediated axillary bud outgrowth. In addition, SL, a plant hormone involved in the repression of shoot branching, acted antagonistically to both gibberellin and CK in the control of lateral bud outgrowth. Consistent with this, the expression of JcMAX2, a J. curcas homolog of Arabidopsis MORE AXILLARY GROWTH 2 encoding an F-box protein in the SL signaling pathway, was repressed by gibberellin and CK treatment. We also provide physiological evidence that gibberellin also induces shoot branching in many other trees, such as papaya, indicating that a more complicated regulatory network occurs in the control of shoot branching in some perennial woody plants.

Axillary buds are dwarfed shoots that tightly regulate GA pathway and GA-inducible 1,3-β-glucanase genes during branching in hybrid aspen

“…The importance of GA levels in AXBs themselves is demonstrated by the up-regulation of GA biosynthesis genes in AXBs of hybrid aspen that are released from dormancy by chilling (Rinne et al , 2011). In support of this, GA supply also induces branching in a number of woody species (Saure, 1985; Rinne et al , 2011; Ni et al , 2015). AXBs of hybrid aspen resemble short day (SD)-induced terminal buds (TBs), both morphologically and molecularly (Rinne et al , 2015), although their vascularization might initially differ (Pizzolato and Larson, 1977).…”

Overexpression of a tomato miR171 target gene SlGRAS24 impacts multiple agronomical traits via regulating gibberellin and auxin homeostasis

“…Here, we demonstrate that tomato SlGRAS24 is a key transcription factor for coordinated regulation of GA and auxin signalling pathways, which may provide clues to the mechanisms underlying the significantly increased height of Atham1, 2, 3 mutant plants and their shorter primary roots (Engstrom et al ., ; Wang et al ., ). Atham1, 2, 3 mutant plants also have altered lateral branch formation (Schulze et al ., ; Wang et al ., ), a process which is also regulated by auxin and GA (Martínez‐Bello et al ., ; Müller and Leyser, ; Ni et al ., ). Recently, it was found that overexpression of a sunflower ( Helianthus annuus L.) GRAS‐ like gene altered the GA content and axillary meristem outgrowth of transgenic Arabidopsis plants (Fambrini et al ., ).…”

Gibberellin repression of axillary bud formation in Arabidopsis by modulation of DELLA‐SPL9 complex activity

“…However, how the DELLA-SPL9 complex performs different functions on different target genes remains to be elucidated. Ni et al showed that gibberellin is a positive regulator in controlling axillary bud outgrowth in the perennial woody plant Jatropha curcas (Ni et al 2015). In strawberry, when FveGA20ox4 is mutated, axillary meristems are still dormant, the number of inflorescences is increased in the plant, and GA biosynthesis in the axillary meristem is necessary for inducing stolon differentiation (Tenreira et al 2017).…”