Molecular Dissection Unveiling Dwarfing Effects of Plant Growth Retardants on Pomegranate.

Jingjing Qian,Wenxu Ren,Nengbing Hu,Yuchen Yang,Ning Wang,Xiyao Hong,Lingyue Chen,Rufan Zhang,Yingjie Shu,Kaijing Zhang

doi:10.3389/fpls.2022.866193

Abstract

Dwarfed stature is a desired trait for modern orchard production systems. One effective strategy for dwarfing cultivation is exogenously applying plant growth retardants (PGRs) to plants. However, for many economic fruit trees, the current knowledge on the regulatory mechanisms underlying the dwarfing effect of PGRs is limited, which largely restricts the agricultural application of PGRs. In this study, we exogenously applied three kinds of PGRs [paclobutrazol, daminozide (B9), and mannitol] to the seedlings of pomegranate (Punica granatum L.) and performed comparative transcriptome analysis to elucidate the molecular features of PGR-induced dwarfing in pomegranates. Our results showed that all the three PGRs could significantly suppress plant growth of pomegranate. The inhibition of auxin biosynthetic processes, as well as auxin-mediated shoot development, may be considered as the main reason for the dwarfing. Besides that, different PGRs were also found to induce dwarfing via specific mechanisms, for example, cellular response to strigolactone was particularly suppressed by the application of paclobutrazol, while the level of carbohydrate homeostasis and metabolism were downregulated in conditions of either B9 or mannitol treatments. Furthermore, exogenous PGR application was supposed to cause adverse impacts on the normal physiological process of pomegranate seedlings, which may bring extra burden to pomegranate plants. These novel findings unveiled the genetic basis underlying the dwarfing in pomegranates, which provides deeper insights into PGR-mediated dwarfing cultivation of pomegranates.

Highlights

For modern orchards, dwarfed stature is a favorable agronomic trait of economic fruit trees, which reduces the nutrients that plants spend on shoots and leaves and promotes flower blooming and fruit growing
These results suggested that, besides dwarfing, these exogenous plant growth retardants” (PGRs) supplies may lead to adverse impacts on plant normal physiological status
We dissected the molecular mechanisms underlying PGR-induced dwarfing in pomegranates

Summary

Introduction

For modern orchards, dwarfed stature is a favorable agronomic trait of economic fruit trees, which reduces the nutrients that plants spend on shoots and leaves and promotes flower blooming and fruit growing. PGR-Induced Dwarfing Mechanisms in Pomegranate used strategies for plant dwarfing, such as breeding dwarf varieties (Patzak et al, 2012; Ma et al, 2014; Wang et al, 2018), grafting using certain rootstocks or interstocks (Sugar and Mielke, 2002; Foster et al, 2015, 2017), and applying exogenous plant growth regulators (Koukourikou-Petridou, 1996; Zhang et al, 2018, 2020; Shi et al, 2021). Exogenous application of growth regulators overcomes the shortcomings of lacking background knowledge and mature breeding system and shows apparent benefits in reducing the length and endeavors of cultivations. Many plant growth regulators involved in cell division and elongation have shown their successes in dwarfing, such as brassinosteroid (BR), cytokinin, paclobutrazol, and daminozide (B9) (Koukourikou-Petridou, 1996; Zhang et al, 2018, 2020; Dong et al, 2019; Shi et al, 2021). A better understanding of the genes and pathways related to PGR-induced dwarfing could provide clues for molecular-assisted screening and breeding of dwarfing varieties in the future

Methods

Results

Discussion

Conclusion