Fruit brown rot caused by Monilinia spp. is the most important fungal disease of stone fruits worldwide. Several phenotyping protocols to accurately characterize and evaluate brown rot infection have been proposed; however, the outcomes from those studies have not led to consistent advances in resistance breeding programs. Breeding for disease resistance is one of the most challenging objectives for crop improvement because disease expression is tetrahedral: it is simultaneously influenced by agent, host, environment, and human management. The present study presents a strategy based on Bayesian inference to analyze a peach breeding progeny for resistance to brown rot, evaluated using a polytomous ordinal scale. A pedigree containing two sources of resistance, one from peach and the other from almond, several commercial cultivars, and two segregating populations were analyzed to estimate the narrow-sense heritability (h² ) and breeding values (EBVs) for brown rot resistance in progenies. Results show promise for genetic improvement of disease resistance and other traits characterized by strong environmental interactions.

Noninfectious bud-failure (BF) remains a major threat to almond production in California, particularly with the recent rapid expansion of acreage and as more intensive cultural practices and modern cultivars are adopted. BF has been shown to be inherited in both vegetative and sexual progeny, with exhibition related to the age and propagation history of scion clonal sources. These characteristics suggest an epigenetic influence, such as the loss of juvenility mediated by DNA-(de)methylation. Various degrees of BF have been reported among cultivars as well as within sources of clonal propagation of the same cultivar. Genome-wide methylation profiles for different clones within almond genotypes were developed to examine their association with BF levels and association with the chronological time from initial propagation. The degree of BF exhibition was found to be associated with DNA-(de)methylation and clonal age, which suggests that epigenetic changes associated with ageing may be involved in the differential exhibition of BF within and among almond clones. Research is needed to investigate the potential of DNA-(de)methylation status as a predictor for BF as well as for effective strategies to improve clonal selection against age related deterioration. This is the first report of an epigenetic-related disorder threatening a major tree crop.

While all organisms age, our understanding of how aging occurs varies among species. The aging process in perennial plants is not well-defined, yet can have implications on production and yield of valuable fruit and nut crops. Almond exhibits an age-related disorder known as non-infectious bud failure (BF) that affects vegetative bud development, indirectly affecting kernel yield. This species and disorder present an opportunity to address aging in a commercially relevant and vegetatively propagated perennial crop. The hypothesis tested in this study was that relative telomere length and/or telomerase reverse transcriptase (TERT) expression can serve as biomarkers of aging in almond. Relative telomere lengths and expression of TERT, a subunit of the enzyme telomerase, were measured via qPCR methods using bud and leaf samples collected from distinct age cohorts over a two-year period. Results from this work show a marginal but significant association between both relative telomere length and TERT expression, and age, suggesting that as almonds age, telomeres shorten and TERT expression decreases. This work provides information on potential biomarkers of perennial plant aging, contributing to our knowledge of this process. In addition, these results provide opportunities to address BF in almond breeding and nursery propagation.

Abstract Background Peach [Prunus persica (L.) Batsch] is an economically important fruit crop that has become a genetic-genomic model for all Prunus species in the family Rosaceae. A doubled haploid reference genome sequence length of 227.3 Mb, a narrow genetic base contrasted by a wide phenotypic variability, the generation of cultivars through hybridization with subsequent clonal propagation, and the current accessibility of many founder genotypes, as well as the pedigree of modern commercial cultivars make peach a model for the study of inter-cultivar genomic heterogeneity and its shaping by artificial selection. Results The quantitative genomic differences among the three genotypes studied as genomic variants, included small variants (SNPs and InDels) and structural variants (SV) (duplications, inversions and translocations). The heirloom cultivar 'Georgia Belle’ and an almond by peach introgression breeding line 'F8,1-42’ are more heterogeneous than is the modern cultivar 'Dr. Davis’ when compared to the peach reference genome ('Lovell’). A pair-wise comparison of consensus genome sequences with 'Lovell’ showed that 'F8,1-42’ and 'Georgia Belle’ were more divergent than were 'Dr. Davis’ and 'Lovell’. Conclusions A novel application of emerging bioinformatics tools to the analysis of ongoing genome sequencing project outputs has led to the identification of a range of genomic variants. Results can be used to delineate the genomic and phenotypic differences among peach genotypes. For crops such as fruit trees, the availability of old cultivars, breeding selections and their pedigrees, make them suitable models for the study of genome shaping by artificial selection. The findings from the study of such genomic variants can then elucidate the control of pomological traits and the characterization of metabolic pathways, thus facilitating the development of protocols for the improvement of Prunus crops.

Almond [Prunus dulcis (Mill.) D.A. Webb] is an economically important, specialty nut crop grown almost exclusively in the United States. Breeding and improvement efforts worldwide have led to the development of key, productive cultivars, including 'Nonpareil,' which is the most widely grown almond cultivar. Thus far, genomic resources for this species have been limited, and a whole-genome assembly for 'Nonpareil' is not currently available despite its economic importance and use in almond breeding worldwide. We generated a 571X coverage genome sequence using Illumina, PacBio, and optical mapping technologies. Gene prediction revealed 49,321 putative genes using MinION Oxford nanopore and Illumina RNA sequencing, and genome annotation found that 68% of predicted models are associated with at least one biological function. Furthermore, epigenetic signatures of almond, namely DNA cytosine methylation, have been implicated in a variety of phenotypes including self-compatibility, bud dormancy, and development of noninfectious bud failure. In addition to the genome sequence and annotation, this report also provides the complete methylome of several almond tissues, including leaf, flower, endocarp, mesocarp, exocarp, and seed coat. Comparisons between methylation profiles in these tissues revealed differences in genome-wide weighted % methylation and chromosome-level methylation enrichment.

Almond [Prunus dulcis (Mill.) D.A. Webb] is an economically important nut crop susceptible to the genetic disorder, Non-infectious Bud Failure (NBF). Despite the severity of exhibition in several prominent almond cultivars, no causal mechanism has been identified underlying NBF development. The disorder is hypothesized to be associated with differential DNA methylation patterns based on patterns of inheritance (i.e., via sexual reproduction and clonal propagation) and previous work profiling methylation in affected trees. Peach (Prunus persica L. Batsch) is a closely related species that readily hybridizes with almond; however, peach is not known to exhibit NBF. A cross between an NBF-exhibiting 'Carmel' cultivar and early flowering peach ('40A17') produced an F₁ where ∼50% of progeny showed signs of NBF, including canopy die-back, erratic branching patterns (known as "crazy-top"), and rough bark. In this study, whole-genome DNA methylation profiles were generated for three F₁ progenies exhibiting NBF and three progenies considered NBF-free. Subsequent alignment to both the almond and peach reference genomes showed an increase in genome-wide methylation levels in NBF hybrids in CG and CHG contexts compared to no-NBF hybrids when aligned to the almond genome but no difference in methylation levels when aligned to the peach genome. Significantly differentially methylated regions (DMRs) were identified by comparing methylation levels across the genome between NBF- and no-NBF hybrids in each methylation context. In total, 115,635 DMRs were identified based on alignment to the almond reference genome, and 126,800 DMRs were identified based on alignment to the peach reference genome. Nearby genes were identified as associated with the 39 most significant DMRs occurring either in the almond or peach alignments alone or occurring in both the almond and peach alignments. These DMR-associated genes include several uncharacterized proteins and transposable elements. Quantitative PCR was also performed to analyze the gene expression patterns of these identified gene targets to determine patterns of differential expression associated with differential DNA methylation. These DMR-associated genes, particularly those showing corresponding patterns of differential gene expression, represent key targets for almond breeding for future cultivars and mitigating the effects of NBF-exhibition in currently affected cultivars.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection has led to a global health crisis, and yet our understanding of the disease pathophysiology and potential treatment options remains limited. SARS-CoV-2 infection occurs through binding and internalization of the viral spike protein to angiotensin converting enzyme 2 (ACE2) on the host cell membrane. Lethal complications are caused by damage and failure of vital organs that express high levels of ACE2, including the lungs, the heart and the kidneys. Here, we established a high-throughput drug screening strategy to identify therapeutic candidates that reduce ACE2 levels in human embryonic stem cell (hESC) derived cardiac cells. Drug target analysis of validated hit compounds, including 5 alpha reductase inhibitors, revealed androgen signaling as a key modulator of ACE2 levels. Treatment with the 5 alpha reductase inhibitor dutasteride reduced ACE2 levels and internalization of recombinant spike receptor binding domain (Spike-RBD) in hESC-derived cardiac cells and human alveolar epithelial cells. Finally, clinical data on coronavirus disease 2019 (COVID-19) patients demonstrated that abnormal androgen states are significantly associated with severe disease complications and cardiac injury as measured by blood troponin T levels. These findings provide important insights on the mechanism of increased disease susceptibility in male COVID-19 patients and identify androgen receptor inhibition as a potential therapeutic strategy.

The availability of a complete peach genome assembly and three different peach genome sequences created by our group provide new opportunities for application of genomic data and can improve the power of the classical Quantitative Trait Loci (QTL) approaches to identify candidate genes for peach disease resistance. Brown rot caused by Monilinia spp., is the most important fungal disease of stone fruits worldwide. Improved levels of peach fruit rot resistance have been identified in some cultivars and advanced selections developed in the UC Davis and USDA breeding programs. Whole genome sequencing of the Pop-DF parents lead to discovery of high-quality SNP markers for QTL genome scanning in this experimental population. Pop-DF created by crossing a brown rot moderately resistant cultivar 'Dr. Davis' and a brown rot resistant introgression line, 'F8,1-42', derived from an initial almond × peach interspecific hybrid, was evaluated for brown rot resistance in fruit of harvest maturity over three seasons. Using the SNP linkage map of Pop-DF and phenotypic data collected with inoculated fruit, a genome scan for QTL identified several SNP markers associated with brown rot resistance. Two of these QTLs were placed on linkage group 1, covering a large (physical) region on chromosome 1. The genome scan for QTL and SNP effects predicted several candidate genes associated with disease resistance responses in other host-pathogen systems. Two potential candidate genes, ppa011763m and ppa026453m, may be the genes primarily responsible for M. fructicola recognition in peach, activating both PAMP-triggered immunity (PTI) and effector-triggered immunity (ETI) responses. Our results provide a foundation for further genetic dissection, marker assisted breeding for brown rot resistance, and development of peach cultivars resistant to brown rot.

Cell adhesion molecules are ubiquitous in multicellular organisms, specifying precise cell-cell interactions in processes as diverse as tissue development, immune cell trafficking and the wiring of the nervous system^1-4. Here we show that a wide array of synthetic cell adhesion molecules can be generated by combining orthogonal extracellular interactions with intracellular domains from native adhesion molecules, such as cadherins and integrins. The resulting molecules yield customized cell-cell interactions with adhesion properties that are similar to native interactions. The identity of the intracellular domain of the synthetic cell adhesion molecules specifies interface morphology and mechanics, whereas diverse homotypic or heterotypic extracellular interaction domains independently specify the connectivity between cells. This toolkit of orthogonal adhesion molecules enables the rationally programmed assembly of multicellular architectures, as well as systematic remodelling of native tissues. The modularity of synthetic cell adhesion molecules provides fundamental insights into how distinct classes of cell-cell interfaces may have evolved. Overall, these tools offer powerful abilities for cell and tissue engineering and for systematically studying multicellular organization.

SARS-CoV-2 infection has led to a global health crisis, and yet our understanding of the disease and potential treatment options remains limited. The infection occurs through binding of the virus with angiotensin converting enzyme 2 (ACE2) on the cell membrane. Here, we established a screening strategy to identify drugs that reduce ACE2 levels in human embryonic stem cell (hESC)-derived cardiac cells and lung organoids. Target analysis of hit compounds revealed androgen signaling as a key modulator of ACE2 levels. Treatment with antiandrogenic drugs reduced ACE2 expression and protected hESC-derived lung organoids against SARS-CoV-2 infection. Finally, clinical data on COVID-19 patients demonstrated that prostate diseases, which are linked to elevated androgen, are significant risk factors and that genetic variants that increase androgen levels are associated with higher disease severity. These findings offer insights on the mechanism of disproportionate disease susceptibility in men and identify antiandrogenic drugs as candidate therapeutics for COVID-19.