Gibberellin acid 4 and 7 increase indole-3-acetic acid production and induce cell division via PbCRF4-mediated activation of PbYUCCA6 expression in ‘Dangshansu’ pear

Abstract

The role of gibberellins in inducing cell division is now widely recognized; however, the underlying mechanisms remain to be clarified. Here, we demonstrate that gibberellin acid 4 and 7 (GA4+7) can induce active cell division leading to ovary expansion as CPPU (N-(2‑chloro-4-pyridyl)-N’-phenylurea) at the early fruit setting stage in ‘Dangshansu’ pear (Pyrus bretshneideri Rehd.). Transcriptomic analysis showed PbCYTOKININ RESPONSE FACTOR4 (PbCRF4) was activated in response to GA4+7 and CPPU, suggesting a candidate gene correlated to gibberellin-induced cell division during early fruit development. Overexpression and RNA interference of PbCRF4 in pear calli demonstrated a role of PbCRF4 in regulating fruit cell proliferation and increased indole-3-acetic acid (IAA) biosynthesis. Ectopic overexpression of PbCRF4 in tomato produced flat fruits with no pointed tips, decreased the fruit index, and increased the pericarp thickness and IAA content. Silencing of SlCRF4 in tomato led to pointed-tip fruits with a relatively low IAA content and reduced pericarp thickness. Furthermore, PbCRF4 transcriptionally activated indole-3-pyruvate monooxygenase 6 (YUCCA6) to increase IAA content in pear. Taken together, this study reveals that GA4+7 induces cell division and an increase in IAA content via regulating PbCRF4 to activate the expression of PbYUCCA6, thereby contributing to the control of fruit shape.