The separation of germ cell populations from the soma is part of the evolutionary transition to multicellularity. Only genetic information present in the germ cells will be inherited by future generations, and any molecular processes affecting the germline genome are therefore likely to be passed on. Despite its prevalence across taxonomic kingdoms, we are only starting to understand details of the underlying micro-evolutionary processes occurring at the germline genome level. These include segregation, recombination, mutation and selection and can occur at any stage during germline differentiation and mitotic germline proliferation to meiosis and post-meiotic gamete maturation. Selection acting on germ cells at any stage from the diploid germ cell to the haploid gametes may cause significant deviations from Mendelian inheritance and may be more widespread than previously assumed. The mechanisms that affect and potentially alter the genomic sequence and allele frequencies in the germline are pivotal to our understanding of heritability. With the rise of new sequencing technologies, we are now able to address some of these unanswered questions. In this review, we comment on the most recent developments in this field and identify current gaps in our knowledge.
Impaired carbon metabolism and reproductive development constrain crop productivity during heat stress. Reproductive development is energy intensive, and its requirement for respiratory substrates rises as associated metabolism increases with temperature. Understanding how these processes are integrated and the extent to which they contribute to the maintenance of yield during and following periods of elevated temperatures is important for developing climate‐resilient crops. Recent studies are beginning to demonstrate links between processes underlying carbon dynamics and reproduction during heat stress, consequently a summation of research that has been reported thus far and an evaluation of purported associations are needed to guide and stimulate future research. To this end, we review recent studies relating to source–sink dynamics, non‐foliar photosynthesis and net carbon gain as pivotal in understanding how to improve reproductive development and crop productivity during heat stress. Rapid and precise phenotyping during narrow phenological windows will be important for understanding mechanisms underlying these processes, thus we discuss the development of relevant high‐throughput phenotyping approaches that will allow for more informed decision‐making regarding future crop improvement.
Wheat is one of the most important crops in the world; however, loss of genetic variability and abiotic stress caused by variable climatic conditions threaten future productivity. Reproduction is critical for wheat yield; however, pollen development is amongst the developmental stages most sensitive to stresses such as heat, cold, or drought. A better understanding of how anther and pollen development is regulated is needed to help produce more resilient crops and ensure future yield increases. However, in cereals such as wheat, barley, and rice, flowers form within the developing pseudostem and therefore accurate staging of floral materials is extremely challenging. This makes detailed phenotypic and molecular analysis of floral development very difficult, particularly when limited plant material is available, for example with mutant or transgenic lines. Here we present an accurate approach to overcome this problem, by non-destructive staging of reproduction development in Cadenza, the widely used spring wheat research variety. This uses a double-scale system whereby anther and pollen development can be predicted in relation to spike size and spike position within the pseudostem. This system provides an easy, reproducible method that facilitates accurate sampling and analysis of floral materials, to enable anther and pollen developmental research.
Pollen development has dependency on the tapetum, a sporophytic anther cell layer surrounding the microspores, which functions in pollen wall formation, but is also essential for meiosis-associated development. There is clear evidence of crosstalk and co-regulation between the tapetum and microspores, however how this is achieved is currently not characterised. ABORTED MICROSPORES (AMS), a tapetum transcription factor, is important for pollen wall formation, but also has an undefined role in early pollen development. We conducted a detailed investigation of chromosome behaviour, cytokinesis, radial microtubule array (RMA) organisation and callose formation in the ams mutant. Early meiosis initiates normally in ams, shows delayed progression after the pachytene stage, and then fails during late meiosis, with disorganised RMA, defective cytokinesis, abnormal callose formation and microspore degeneration, alongside abnormal tapetum development. Here, we show that selected meiosis-associated genes are directly repressed by AMS, and that AMS is essential for late meiosis progression. Our findings indicate that AMS has a dual function in tapetum-meiocyte crosstalk by playing an important regulatory role during late meiosis, in addition to its previously characterised role in pollen wall formation. AMS is critical for RMA organisation, callose deposition and therefore cytokinesis and is involved in the crosstalk between the gametophyte and sporophytic tissues, which enables synchronous development of tapetum and microspores.
ROOT UV-B SENSITIVE4 (RUS4) encodes a protein with no known function that contains a conserved Domain of Unknown Function 647 (DUF647). The DUF647-containing proteins RUS1 and RUS2 have previously been associated with root UV-B-sensing pathway that plays a major role in Arabidopsis early seedling morphogenesis and development. Here, we show that RUS4 knockdown Arabidopsis plants, referred to as amiR-RUS4, were severely reduced in male fertility with indehiscent anthers. Light microscopy of anther sections revealed a significantly reduced secondary wall thickening in the endothecium of amiR-RUS4 anthers. We further show that the transcript abundance of the NAC domain genes NAC SECONDARY WALL THICKENING PROMOTING FACTOR1 (NST1) and NST2, which have been shown to regulate the secondary cell wall thickenings in the anther endothecium, were dramatically reduced in the amiR-RUS4 floral buds. Expression of the secondary cell wall-associated MYB transcription factor genes MYB103 and MYB85 were also strongly reduced in floral buds of the amiR-RUS4 plants. Overexpression of RUS4 led to increased secondary thickening in the endothecium. However, the rus4-2 mutant exhibited no obvious phenotype. Promoter-GUS analysis revealed that the RUS4 promoter was highly active in the anthers, supporting its role in anther development. Taken together, these results suggest that RUS4, probably functions redundantly with other genes, may play an important role in the secondary thickening formation in the anther endothecium by indirectly affecting the expression of secondary cell wall biosynthetic genes.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.