Carmeli-Weissberg, M. | Search bioRxiv

bioRxiv2023

Alleviating the barrier of adventitious roots formation in recalcitrant mature tissue by slow release of a synthetic auxin

Clonal propagation of plants by induction of adventitious roots (ARs) from stem cuttings is a requisite step in breeding programs. A major barrier exists for propagating valuable plants that naturally have low capacity to form ARs. Due to the central role of auxin in organogenesis, indole-3-butyric acid (IBA) is often used as part of commercial rooting mixtures, yet many recalcitrant plants do not form ARs in response to this treatment. Here, we describe the synthesis and screening of a focused library of synthetic auxin conjugates in Eucalyptus grandis cuttings and identify 4-chlorophenoxyacetic acid-L-tryptophan-OMe as a competent enhancer of adventitious rooting in a number of recalcitrant woody plants, including apple and argan. Comprehensive metabolic and functional analyses reveal that this activity is engendered by prolonged auxin signaling due to initial fast uptake and slow release and clearance of the free auxin 4-chlorophenoxyacetic acid. This work highlights the utility of a slow-release strategy for bioactive compounds for more effective plant growth regulation.

plant biology↗

bioRxiv2022

Abscisic acid plays a key role in the regulation of date palm fruit ripening

The date palm (Phoenix dactylifera L.) fruit is of major importance for the nutrition of broad populations in the worlds desert strip; yet this crop is sorely understudied. Understanding the mechanisms regulating date fruit development and ripening is essential to customise this crop to the climatic change, which elaborates yield losses due to often too early occurring wet season. This study aimed to elucidate the mechanism regulating date fruit ripening. To that end, we followed the natural process of date fruit development and the effects of exogenous hormone application on fruit ripening in the elite cultivar Medjool. The results of the current study indicate that the onset of fruit ripening occurred once the seed had reached maximum dry weight. From this point until fruit harvest, the pulp endogenous abscisic acid (ABA) turned up and its levels consistently increased. The final stage in fruit ripening, the yellow-to-brown transition, was preceded by an arrest of xylem-mediated water transport into the fruit. Exogenous ABA application enhanced fruit ripening when applied just prior to the green-to-yellow fruit color transition. Repeated ABA applications hastened all fruit ripening processes, resulting in a significantly earlier harvest. The emerging pivotal role of ABA in the regulation of date fruit ripening is thoroughly discussed. HighlightsThe plant hormone abscisic acid (ABA) promotes date fruit ripening, as indicated by the enhanced change in fruit color, from green to yellow, and the enhanced rate of sugar accumulation.

plant biology↗