Revolutionizing plant propagation with synthetic auxin

Plant propagation stands as a cornerstone practice in agriculture, essential for cultivating the diversity of crops. This age-old practice involves creating new plants from existing specimens, ensuring the continuation and multiplication of species and varieties. Propagation techniques span from the simple sowing of seeds to sophisticated methods like grafting, stem cuttings, and tissue culture. Each method plays a pivotal role in agriculture, enabling the replication of desirable plant traits, the preservation of genetic diversity, and the efficient production of crops.

One of the long-standing hurdles in agriculture and horticulture has been the propagation of valuable woody plants. These plants often resist rooting from stem cuttings, a key step in clonal (vegetative) propagation. This challenge is particularly pronounced in recalcitrant woody species, notoriously difficult to coax into forming new roots.

At the heart of plant propagation lies auxin, a vital plant hormone that orchestrates growth and development processes ranging from cell elongation to the formation of roots. Auxins also play a pivotal role in enabling cuttings from a parent plant to establish new roots, a property that has been harnessed for agricultural advancements. However, not all plants are equally responsive to natural auxins, leaving a significant gap in our ability to propagate certain species efficiently.

A recent study published in Nature Biotechnology presents an innovative approach to overcoming this propagation barrier. The novel approach involves the synthesis and application of a synthetic auxin conjugate, specifically designed to mimic the effects of natural auxin but with enhanced efficiency and longevity. This synthetic auxin, named 4-chlorophenoxyacetic acid–L-tryptophan-OMe, demonstrates remarkable effectiveness in inducing root formation in species that traditionally resist rooting, such as Eucalyptus grandis, apple, and argan trees.

The efficiency of this synthetic auxin apparently lies in its slow-release mechanism. Unlike its natural counterparts, which are rapidly metabolized and cleared from plant tissues, this synthetic variant ensures a prolonged presence within the plant, maintaining a consistent stimulatory signal for root formation. This slow and steady release not only maximizes the auxin’s availability but also minimizes any potential stress or toxicity to the plant, fostering a conducive environment for root development.

Solid-Supported Membrane Electrophysiology (SSME) experiments conducted with the SURFE2R system revealed that, unlike native auxin, the synthetic variant is not transported by the PIN-FORMED8 (PIN8) auxin exporter, suggesting the involvement of another uncharacterized efflux transporter. At the same time, both native and synthetic auxins were found to utilize the native auxin importer AUX1, as revealed by HPLC–MS/MS quantification.

Overall, the study shows that the new synthetic auxin significantly enhances rooting rates in cuttings from various hard-to-root tree species. The study provides an industry-compatible application method with high commercial potential across multiple sectors like agriculture, horticulture, and forestry. Furthermore, the slow-release approach used here can also be integrated into other agricultural practices involving auxin to improve plant growth and fruit production.

Find the original article here: https://www.nature.com/articles/s41587-023-02065-3

Learn more about Solid Supported Membrane-Based Electrophysiology and SURFE²R devices here: https://www.nanion.de/products/surfe2r-n1/