Fine-tuning of quantitative traits

The low-hanging fruits in plant breeding were harvested a long time ago.Now is the time for optimizing the desired traits,which often requires minor but significant changes in quantitative traits.Quantitative traits can be affected by slight changes in expression levels.However,genetic variation in gene-regulatory regions may be rare and difficult to identify(Rodríguez-Leal et al.,2017).Therefore,methods to induce gradual changes in gene expression are highly warranted.

Plasma Membrane H^＋-ATPase Regulation in the Center of Plant Physiology

The plasma membrane （PM） H^＋-ATPase is an important ion pump in the plant cell membrane. By extruding protons from the cell and generating a membrane potential, this pump energizes the PM, which is a prerequisite for growth. Modification of the autoinhibitory terminal domains activates PM H^＋-ATPase activity, and on this basis it has been hypothesized that these regulatory termini are targets for physiological factors that activate or inhibit proton pumping. In this review, we focus on the posttranslational regulation of the PM H＋-ATPase and place regulation of the pump in an evolutionary and physiological context. The emerging picture is that multiple signals regulating plant growth interfere with the posttranslational regulation of the PM H^＋-ATPase.

Plant ABC Transporters Enable Many Unique Aspects of a Terrestrial Plant＇s Lifestyle

Terrestrial plants have two to four times more ATP-binding cassette （ABC） transporter genes than other organisms, including their ancestral microalgae. Recent studies found that plants harboring mutations in these transporters exhibit dramatic phenotypes, many of which are related to developmental processes and functions necessary for life on dry land. These results suggest that ABC transporters multiplied during evolution and assumed novel functions that allowed plants to adapt to terrestrial environmental conditions. Examining the literature on plant ABC transporters from this viewpoint led us to propose that diverse ABC transporters enabled many unique and essential aspects of a terrestrial plant＇s lifestyle, by transporting various compounds across specific membranes of the plant.

Controlling flowering of Medicago sativa(alfalfa)by inducing dominant mutations

Breeding plants with polyploid genomes is challenging because functional redundancy hampers the identification of loss-of-function mutants.Medicago sativa is tetraploid and obligate outcrossing,which together with inbreeding depression complicates traditional breeding approaches in obtaining plants with a stable growth habit.Inducing dominant mutations would provide an alternative strategy to introduce domestication traits in plants with high gene redundancy.Here we describe two complementary strategies to induce dominant mutations in the M.sativa genome and how they can be relevant in the control of flowering time.First,we outline a genome-engineering strategy that harnesses the use of microProteins as developmental regulators.MicroProteins are small proteins that appeared during genome evolution from genes encoding larger proteins.Genomeengineering allows us to retrace evolution and create microProtein-coding genes de novo.Second,we provide an inventory of genes regulated by microRNAs that control plant development.Making respective gene transcripts microRNA-resistant by inducing point mutations can uncouple microRNA regulation.Finally,we investigated the recently published genomes of M.sativa and provide an inventory of breeding targets,some of which,when mutated,are likely to result in dominant traits.

Gene-editing in plants no longer requires tissue culture

Plant gene editing,which can produce targeted modifications in plants,shows great potential for gene function analysis and precision breeding of crops[1].To produce gene-edited plants,gene editing reagents[2](for example,CRISPR/Cas9 components)need to be delivered to plant cells.This involves a lengthy,costly and labor-intensive tissue culture step,which,moreover,is currently only possible in limited number of plant species.