Identification of genes involved in male sterility in wheat (Triticum aestivum L.) which could be used in a genic hybrid breeding system

Abstract

Wheat is grown on more land than any other crop in the world. Current estimates suggest that yields will have to increase sixty percent by 2050 to meet the demand of an ever‐increasing human population; however, recent wheat yield gains have lagged behind other major crops such as rice and maize. One of the reasons suggested for the lag in yield potential is the lack of a robust hybrid system to harness the potential yield gains associated with heterosis, also known as hybrid vigor. Here, we set out to identify candidate genes for a genic hybrid system in wheat and characterize their function in wheat using RNASeq on stamens and carpels undergoing meiosis. Twelve genes were identified as potentially playing a role in pollen viability. CalS5‐ and RPG1‐like genes were identified as pre‐ and post‐meiotic genes for further characterization and to determine their role in pollen viability. It appears that all three homoeologues of both CalS5 and RPG1 are functional in wheat as all three homoeologues need to be knocked out in order to cause male sterility. However, one functional homoeologue is sufficient to maintain male fertility in wheat.

Turning Up the Temperature on CRISPR: Increased Temperature Can Improve the Editing Efficiency of Wheat Using CRISPR/Cas9

“…Stacking guides also can dramatically help increase the overall levels of mutations and mitigate the differences between mutation rates per guide. Single guide efficiencies can be large, ranging from 0 to 90%, in this work and previous studies targeting homoeologs genes 7 to 45% of plants were edited at a particular locus (Milner et al, 2020).…”

“…Wheat has a relatively low rate of CRISPR/Cas9 editing and it is thought that most are induced during the first few days after transformation. In general, an efficiency of about 10% overall mutation rate is to be expected (Howells et al, 2018;Liu et al, 2019;Zhang et al, 2019;Milner et al, 2020). Recently, we have shown that stacking guides can improve efficiency greatly and help create full knockouts of close to 10% in wheat (Milner et al, 2020).…”

“…In general, an efficiency of about 10% overall mutation rate is to be expected (Howells et al, 2018;Liu et al, 2019;Zhang et al, 2019;Milner et al, 2020). Recently, we have shown that stacking guides can improve efficiency greatly and help create full knockouts of close to 10% in wheat (Milner et al, 2020). Mutations produced early on in transformation have high levels of heritability, but present a problem in the limited time available for mutations to occur.…”

The potential of resilient carbon dynamics for stabilizing crop reproductive development and productivity during heat stress

“…It is plausible that this regulation is linked with the maintenance of sugar content in photosynthesising tissue pre‐ and post‐anthesis, which in turn decelerates the decline in net carbon balance to achieve heat tolerance (Julius et al, 2017; Zhou et al, 2017). Concurrently, SWEET, for example, RPG1 (Milner et al, 2020), and SUC/SUT, for example, SUC1 (Sivitz, Reinders, & Ward, 2008; Xu, Chen, Yunjuan, Chen, & Liesche, 2018), sugar transporters have been implicated in pollen development, most significantly by facilitating water transport out of endothecium cell walls to increase tension and enable pollen dehiscence (Keijzer, 1987; Wilson et al, 2011). Consequently, photosynthetic activity in reproductive structures, especially anthers (Clément & Pacini, 2001), may result in fine‐tuning of sugar transporter activity given elevated temperatures in order to maintain cellular sugar status.…”

Male Fertility Genes in Bread Wheat (Triticum aestivum L.) and Their Utilization for Hybrid Seed Production

“…Similarly, it has been observed that for TaNP1 , the wheat homolog of the rice OsNP1 and maize ZmIPE1 genes encoding a putative glucose-methanol-choline oxidoreductase, knockouts in all three homeologs are required for male sterility [ 34 ]. Milner et al [ 36 ] identified two male fertility genes in wheat, CALS5 - and RPG1-like , through gene expression analysis. Functional analysis of these genes through CRISPR/Cas showed that knockouts in all three homeologs are required to obtain male sterile plants [ 36 ].…”