Gibberellin Signaling Is Required for Far-Red Light-Induced Shoot Elongation in Pinus tabuliformis Seedlings

Abstract

Gibberellin (GA) is known to play an important role in low red/far-red (R:FR) light ratio-mediated hypocotyl and petiole elongation in Arabidopsis (Arabidopsis thaliana). However, the regulatory relationship between low R:FR and GAs remains unclear, especially in gymnosperms. To increase our understanding of the molecular basis of low R:FR-mediated shoot elongation in pines and to determine whether there is an association between low R:FR and GAs action, we explored the morphological and transcriptomic changes triggered by low R:FR, GAs, and paclobutrazol (PAC), a GAs biosynthesis inhibitor, in Pinus tabuliformis seedlings. Transcriptome profiles revealed that low R:FR conditions and GAs have a common set of transcriptional targets in P. tabuliformis. We provide evidence that the effect of low R:FR on shoot elongation in P. tabuliformis is at least partially modulated by GAs accumulation, which can be largely attenuated by PAC. GAs are also involved in the cross talk between different phytohormones in the low R:FR response. A GA biosynthesis gene, encoding entkaurenoic acid oxidase (KAO), was strongly stimulated by low R:FR without being affected by GAs feedback regulation or the photoperiod. We show that GA signaling is required for low R:FR-induced shoot elongation in P. tabuliformis seedlings, and that there are different regulatory targets for low R:FR-mediated GA biosynthesis between conifers and angiosperms.

Control of Plant Growth and Defense by Photoreceptors: From Mechanisms to Opportunities in Agriculture

“…Although shade-avoidance responses are displayed by a wide variety of plant species representing a broad spectrum of growth forms, including wild and cultivated herbaceous plants (Ballare ét al., 1990;Pierik et al, 2004;Kebrom and Brutnell, 2007;Sasidharan et al, 2008;Whipple et al, 2011;Cagnola et al, 2012;Chitwood et al, 2015;Gommers et al, 2017;Molina-Contreras et al, 2019), grasses (Casal et al, 1985;Finlayson et al, 1998;Kebrom and Brutnell, 2007), vines (Izaguirre et al, 2013), and trees (Ritchie, 1997;de la Rosa et al, 1998;Li et al, 2020), in this section we focus mostly on what has been found in Arabidopsis, since this model provides the most advanced mechanistic insight into the topic. To maintain the focus of this review, we concentrate on the core pathways for shade avoidance that often crosstalk with defense.…”

The Current Status of Research on Gibberellin Biosynthesis

“…In the shade avoidance response, growth promotion under a low red/far-red light ratio was associated with enhanced expression of GA20ox genes in Arabidopsis petioles ( Hisamatsu et al. 2005 ), whereas in seedlings of the gymnosperm Pinus tabuliformis , under these conditions, KAO expression was strongly induced ( Li et al. 2020 ).…”

Plant Development and Crop Yield: The Role of Gibberellins

“…In forage crops such as Medicago truncatula GA is used to improve biomass production for land harnessing [ 231 ]. Shade avoidance response is a non-desirable trait in crops, but it may be modulated to increase wood production in Chinese red pine by means of specific GA treatment and light regimes [ 232 ]. Similarly, in hybrid poplar, the production of wood and biofuel can be increased by enhancing the expression of the GA biosynthesis gene GA20ox [ 233 ].…”