Biology subjects

Hollender, C. A.

Publications and source records attributed to Hollender, C. A..

4 recordsLinked to original sources

bioRxiv2024

Working smarter, not harder: silencing LAZY1 in Prunus domestica causes outward, wandering branch orientations with commercial and ornamental applications.

Controlling branch orientation is a central challenge in tree fruit production, as it impacts factors as diverse as light interception, pesticide use, fruit quality, yield, and labor costs. In an attempt to modify branch orientation, growers use many different management practices, including tying branches to wires or applying growth regulator sprays. However, these practices are often costly and ineffective. In contrast, altering the expression of genes that control branch angles and orientations would permanently optimize tree architecture with minimal management inputs. One gene implicated in branch angle control is LAZY1, which promotes upward branch growth in response to gravity. We used an antisense vector to silence LAZY1 in plum (Prunus domestica). We found that these LAZY1-silenced lines have significantly increased branch and petiole angles. In addition, they lack apical dominance and display a "wandering" or weeping branch trajectory. Given these phenotypes, we assessed whether the strength or stiffness of the branches were compromised. No differences were observed in new growth. While the wood of first-year LAZY1-silenced branches was more flexible and weaker than the control, the strength and stiffness of the branches were not decreased because branch diameter is increased. Finally, we evaluated the utility of LAZY1-silenced trees for two planar orchard systems, training them in super slender axe and espalier. LAZY1-silenced trees had more open canopies and were easier to constrain to the trellis height. This work illustrates the power of manipulating gene expression to optimize plant architecture for each horticultural application.

plant biology↗

bioRxiv2023

Genetic factors acting prior to dormancy in sour cherry influence bloom time the following spring

Bloom time is central to tree fruit production, and for Prunus species floral development leading up to bloom spans four seasons. Understanding this entire process is crucial for developing strategies to manipulate bloom time to prevent crop loss due to climate change. Here, we present a detailed examination of flower development from initiation until bloom for early- and late-blooming sour cherries (Prunus cerasus) from a population segregating for a major bloom time QTL on chromosome 4. Using a new staging system, we identified floral buds from early-blooming trees were persistently more advanced than those from late-blooming siblings. A gDNA coverage analysis revealed the late-blooming haplotype of this QTL, k, is located on a subgenome originating from the late-blooming P. fruticosa progenitor. Transcriptome analyses identified a large number of genes within this QTL as differentially expressed between early- and late-blooming trees during the vegetative-to-floral transition. From these, we identified candidate genes for the late bloom phenotype, including multiple transcription factors homologous to REproductive Meristem (REM) B3 domain-containing proteins. Additionally, we determined the basis of k in sour cherry is likely separate from candidate genes found in sweet cherry - suggesting several major regulators of bloom time are located on Prunus chromosome 4. HIGHLIGHTDormancy is a main effector of bloom time in fruit trees. However, developmental, genetic, and transcriptomic analyses indicate differences in flower development before dormancy significantly influence flowering time in cherry.

plant biology↗

bioRxiv2023

Defying Gravity: WEEP promotes negative gravitropism in Prunus persica (peach) shoots and roots by establishing asymmetric auxin gradients

Trees with weeping shoot architectures are valued for their beauty and serve as tremendous resources for understanding how plants regulate posture control. The Prunus persica (peach) weeping phenotype, which has elliptical downward arching branches, is caused by a homozygous mutation in the WEEP gene. Until now, little was known about the function of WEEP protein despite its high conservation throughout Plantae. Here, we present the results of anatomical, biochemical, biomechanical, physiological, and molecular experiments that provide insight into WEEP function. Our data suggest that weeping peach does not have defects in branch structure. Rather, transcriptomes from the adaxial (upper) and abaxial (lower) sides of standard and weeping branch shoot tips revealed flipped expression patterns for genes associated with early auxin response, tissue patterning, cell elongation, and tension wood development. This suggests that WEEP promotes polar auxin transport toward the lower side during shoot gravitropic response, leading to cell elongation and tension wood development. In addition, weeping peach trees exhibited steeper root systems and faster root gravitropic response, just as barley and wheat with mutations in their WEEP homolog EGT2. This suggests that the role of WEEP in regulating lateral organ angles and orientations during gravitropism may be conserved. Additionally, size-exclusion chromatography indicated that WEEP proteins self-oligomerize, like other SAM-domain proteins. This oligomerization may be required for WEEP to function in formation of protein complexes during auxin transport. Collectively, our results from weeping peach provide new insight into polar auxin transport mechanisms associated with gravitropism and lateral shoot and root orientation.

plant biology↗

bioRxiv2023

A chromosome-scale assembly for tetraploid sour cherry (Prunus cerasus L.) 'Montmorency' identifies three distinct ancestral Prunus genomes

BackgroundSour cherry (Prunus cerasus L.) is a valuable fruit crop in the Rosaceae family and a hybrid between progenitors most closely related to extant P. fruticosa (ground cherry) and P. avium (sweet cherry). Sour cherry is an allotetraploid with few genomic resources, so a genome sequence would greatly facilitate the improvement of this crop. In Prunus, two known classes of genes are of particular importance to breeding strategies: the self-incompatibility loci (S-alleles), which determine compatible crosses and are critically important for successful fertilization and fruit set, and the Dormancy Associated MADS-box genes (DAMs), which strongly affect dormancy transitions and flowering time. ResultsHere we report a chromosome-scale genome assembly for sour cherry cultivar Montmorency, the predominant sour cherry cultivar grown in the U.S. We also generated a draft assembly of P. fruticosa to use alongside a published P. avium sequence for syntelog-based subgenome assignments for Montmorency. Using hierarchal k-mer clustering and phylogenomics, we provide compelling evidence this allotetraploid is trigenomic, containing two distinct subgenomes inherited from a P. fruticosa-like ancestor (A and A) and two copies of the same subgenome inherited from a P. avium-like ancestor (BB). We therefore assigned the genome composition of Montmorency to be AABB and show little to no recombination has occurred between progenitor subgenomes (A/A and B). The S-alleles and DAMs in Montmorency and P. fruticosa were manually annotated and demonstrated to support the three subgenome assignments. Lastly, the hybridization event that Montmorency is descended from was estimated to have occurred less than 1.61 million years ago, making sour cherry a relatively recent allotetraploid. ConclusionsThe genome of sour cherry cultivar Montmorency highlights the evolutionary complexity of the genus Prunus. These genomic resources will inform future breeding strategies for sour cherry, comparative genomics in the Rosaceae, and questions regarding neopolyploidy.

genomics↗