Symposium Leiden 09-12-2022

NVPW fall symposium Friday, December 9th, 2022 At: Telders Auditorium, Academy Building, Rapenburg 73, Leiden

09:30 Registration and coffee / tea
09:55 Opening by Remko Offringa
10:00 Charles Underwood – MPI for Plant Breeding, Cologne
Engineering apomixis: clonal seeds approaching the fields
10:35 Martina Juranic – Wageningen UR, Plant Breeding
Cracking apomixis using Mendel’s hawkweeds as a research model
11:10 Elevator pitch by exhibitors *)
11:20 Coffee / tea break
11:40 Kim Boutilier – Wageningen UR, Bioscience
New morphogenic gene alleles for plant regeneration
12:15 Wessel Holtman – Fytagoras BV, Leiden
Doubled haploid technology: from academic knowledge towards a practical
tool for breeders
12:40 Lunch
13:10 General members meeting
13:50 Danny Geelen – HortiCell, Ghent University, Belgium
Adventitious root formation in hypocotyls is controlled by a conserved
cotyledon hypocotyl signaling pathway
14:25 Coffee / tea break
14.55 Sander Hogewoning – Plant Lighting BV, Bunnik
LED-lighting in greenhouses: consequences for photosynthesis, plant
morphology and transpiration.
15:30 Marten Elsinga – Iribov BV, Heerhugowaard
Flow cytometry and its possibilities for tissue culture
16:05 Closing drinks

Summaries of the lectures on the NVPW fall symposium, Friday, December 9th, 2022 Telders Auditorium, Academy Building, Rapenburg 73, Leiden

Engineering apomixis: clonal seeds approaching the fields
Charles Underwood – MPI for Plant Breeding, Cologne

Apomixis is a form of reproduction leading to clonal seeds and offspring that are genetically identical to the maternal plant. While apomixis naturally occurs in hundreds of plant species distributed across diverse plant families, it is absent in major crop species. Apomixis has revolutionary potential in plant breeding, as it could allow the instant fixation and propagation though seeds of any plant genotype, most notably F1 hybrids. Mastering and implementing apomixis would reduce the cost of hybrid seed production, facilitate new types of hybrid breeding, and make it possible to harness hybrid vigor in crops that are not presently cultivated as hybrids. Synthetic apomixis can be engineered by combining modifications of meiosis and fertilization. I will review the current knowledge and highlight a major achievement toward the development of efficient apomictic systems usable in agriculture.

Cracking apomixis using Mendel’s hawkweeds as a research model
Martina Juranić - Wageningen UR, Plant Breeding

It’s a lesser-known fact that after years of working with peas, Gregor Mendel started experimenting with “constant hybrids” in hawkweeds (Hieracium spp., syn. Pilosella), which, unlike peas, breed true through seeds as clones. Today we know that hawkweeds disobey the basic laws of inheritance by bypassing meiosis and fertilization via apomictic reproduction. The promise of apomixis in the fixation and indefinite propagation of a desired genotype has long been recognized; however, only recently have highly sophisticated techniques been developed to unravel the genetic basis of apomixis. Research efforts using the hawkweed as an apomictic model will be discussed during the talk.

New morphogenic gene alleles for plant regeneration
Kim Boutilier, Wageningen UR, Bioscience

Plants are developmentally flexible and can be induced to regenerate new tissues, organs, and even embryos in vitro. This plasticity forms the basis for numerous applications in plant breeding and propagation, including in vitro embryogenesis and organogenesis. Improvements in plant regeneration protocols have largely been made using empirical modification of tissue culture parameters. More recently, a number of transcription factors have been identified that can be used to overcome plant regeneration barriers. However, the use of these so-called morphogenic genes relies on stable or transient expression of gene constructs, which is subject to GMO regulations in many countries. We have used CRISPR-Cas9 mutagenesis to generate novel alleles of two morphogenic genes, BABY BOOM and LEAFY COTYLEDON1, that promote plant regeneration in vitro. The mutated regions are found in evolutionarily conserved non-coding nucleotide sequences, opening up the possibility for finding similar mutations in crop species.

Doubled haploid technology: from academic knowledge towards a practical tool for breeders
Wessel Holtman, Fytagoras BV, Leiden

Protocols for the production of doubled haploid (DH) plants have been developed for many plant species in recent decades. However, DH protocols published from an academic perspective often lack possibilities for practical application. A practical DH protocol for use in breeding also includes the production of sufficient, unique, high-quality DH plants in an efficient way and at reasonable costs. Some hurdles, which Fytagoras solved in this respect, will be discussed in the presentation.

Adventitious root formation in hypocotyls is controlled by a conserved cotyledon hypocotyl signalling pathway
Danny Geelen, HortiCell, Ghent University, Belgium

Adventitious root (AR) formation is an adaptive developmental response that can be triggered by exogenous auxin application. We are using Arabidopsis etiolated hypocotyls and inflorescence stem segments to study the regulatory processes and role of auxin in de novo root organogenesis. To address underlying processes of AR induction, we screened a collection of auxin-like molecules for AR-specific induction. A molecule was identified that massively induces AR in etiolated Arabidopsis seedlings without pronounced effects on primary root growth and lateral root branching. The novel compound hysparin, for hypocotyl-specific adventitious root inducer, does not trigger a typical molecular response of DR5-reporter activation or DII-Venus degradation. In fact, auxin response genes are not activated within the first 8 hours. Instead, hysparin activates the cotyledons in producing a signal that induces AR formation on the elongated hypocotyl. Formation of hypocotyl AR depends on the presence of cotyledons and hysparin does not induce AR locally. As hysparin induces AR on elongated hypocotyls of several other species including tomato and rapeseed, its bioactivity impinges on a conserved cotyledon-hypocotyl communication leading to adventitious rooting. In an approach to reveal what genetic elements are involved in this communication, we found only a few hormone signaling elements contributing to hysparin-mediated AR induction. The findings support the presence of a specific cotyledon signaling route controlling hypocotyl adventitious root induction.

LED-lighting in greenhouses: consequences for photosynthesis, plant morphology and transpiration.
Sander Hogewoning, Plant Lighting BV, Bunnik

High energy prices are driving a rapid transition from HPS lighting to full-LED lighting in greenhouses. LEDs not only save electricity compared with HPS but also have consequences for crop photosynthesis, morphology, and transpiration, dependent on the spectral composition of the LED lighting fixture. This imposes both opportunities and risks for growers. Opportunities arise from the flexibility in light spectrum, allowing manipulation of the crop towards the desired response (e.g., rooting, branching, flowering). However, there are risks as insufficient knowledge may result in the wrong choices. The consequences of the transition from HPS to LED will be discussed.

Flow cytometry and its possibilities for tissue culture
Marten Elsinga – Iribov BV, Heerhugowaard

Flow cytometry (FCM) is a well-established method for the analysis of single cells and finds many applications in research and production across various fields ranging from environmental to medical research. At Iribov, the most commonly used application is the determination of DNA content and ploidy levels of plants. Overall, the use of FCM is not conventional and widespread in plant breeding and tissue culture. The focus of our presentation will be on the added value of FCM in tissue culture applications to support researchers by reducing cost and time. Iribov is a large-scale propagator through tissue culture and uses FCM as a routine analysis for a variety of tissue culture techniques. Our FCM researcher, Marten Elsinga, will present the use of FCM for applications such as quality control of microspores for dihaploid production, determination of transformation efficiency of protoplasts, and the control of microbial contamination in tissue culture.