Project description:Trees with weeping shoot architectures are valued for their beauty and are a resource 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 trees do 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 lateral root gravitropic response. This suggests that WEEP moderates root gravitropism and is essential to establishing the set-point angle of lateral roots from the gravity vector. Additionally, size-exclusion chromatography indicated that WEEP proteins self-oligomerize, like other proteins with sterile alpha motif domains. Collectively, our results from weeping peach provide new insight into polar auxin transport mechanisms associated with gravitropism and lateral shoot and root orientation.
Project description:Prunus persica (peach) trees carrying the ‘Pillar’ or ‘Broomy’ trait (br) have vertically oriented branches caused by loss of function mutations in a gene called TILLER ANGLE CONTROL 1 (TAC1). TAC1 encodes a protein in the IGT gene family that includes LAZY1 and DEEPER ROOTING 1 (DRO1), which regulat lateral branch and root orientations, respectively. Here, we found that some of the native TAC1 alleles in the hexaploid plum species Prunus domestica, which has a naturally more upright stature, contained a variable length trinucleotide repeat within the same exon 3 region previously found to be disrupted in pillar peach trees. RNAi silencing of TAC1 in plum resulted in trees with severely vertical branch orientations similar to those in pillar peaches but with an even narrower profile. In contrast, PpeTAC1 over-expression in plum led to trees with wider branch angles and more horizontal branch orientations. Pillar peach trees and transgenic plum lines exhibited pleiotropic phenotypes including differences in trunk and branch diameter, stem growth, and twisting branch phenotypes. Expression profiling of pillar peach trees revealed differential expression of numerous genes associated with biotic and abiotic stress, hormone responses, plastids, reactive oxygen, and secondary and cell wall metabolism. Collectively, the data provide important clues for understanding TAC1 function and show that alteration of TAC1 expression may have broad applicability to agricultural and ornamental tree industries.
Project description:We performed small RNA deep sequencing and identified 47 peach-specific and 47 known miRNAs or families with distinct expression patterns. Together, the identified miRNAs targeted 80 genes, many of which have not been reported previously. Like the model plant systems, peach has two of the three conserved trans-acting siRNA biogenesis pathways with similar mechanistic features and target specificity. Unique to peach, three of the miRNAs collectively target 49 MYBs, 19 of which are known to regulate phenylpropanoid metabolism, a key pathway associated with stone hardening and fruit color development, highlighting a critical role of miRNAs in regulation of peach fruit development and ripening. We also found that the majority of the miRNAs were differentially regulated in different tissues, in part due to differential processing of miRNA precursors. Up to 16% of the peach-specific miRNAs were differentially processed from their precursors in a tissue specific fashion, which has been rarely observed in plant cells. The miRNA precursor processing activity appeared not to be coupled with its transcriptional activity but rather acted independently in peach. Collectively, the data characterizes the unique expression pattern and processing regulation of peach miRNAs and demonstrates the presence of a complex, multi-level miRNA regulatory network capable of targeting a wide variety of biological functions, including phenylpropanoid pathways which play a multifaceted spatial-temporal role in peach fruit development. Identification of peach miRNAs and their targets from four different tissues
Project description:We performed small RNA deep sequencing and identified 47 peach-specific and 47 known miRNAs or families with distinct expression patterns. Together, the identified miRNAs targeted 80 genes, many of which have not been reported previously. Like the model plant systems, peach has two of the three conserved trans-acting siRNA biogenesis pathways with similar mechanistic features and target specificity. Unique to peach, three of the miRNAs collectively target 49 MYBs, 19 of which are known to regulate phenylpropanoid metabolism, a key pathway associated with stone hardening and fruit color development, highlighting a critical role of miRNAs in regulation of peach fruit development and ripening. We also found that the majority of the miRNAs were differentially regulated in different tissues, in part due to differential processing of miRNA precursors. Up to 16% of the peach-specific miRNAs were differentially processed from their precursors in a tissue specific fashion, which has been rarely observed in plant cells. The miRNA precursor processing activity appeared not to be coupled with its transcriptional activity but rather acted independently in peach. Collectively, the data characterizes the unique expression pattern and processing regulation of peach miRNAs and demonstrates the presence of a complex, multi-level miRNA regulatory network capable of targeting a wide variety of biological functions, including phenylpropanoid pathways which play a multifaceted spatial-temporal role in peach fruit development.
Project description:Plum pox virus (PPV) causes the serious sharka disease in Prunus trees. Peach [P. persica (L.) Batsch] trees are severely affected by PPV and no definitive source of genetic resistance has been identified at this moment. Previous results showed, however, that PPV-resistant ‘Garrigues’ almond [P. dulcis (Mill.) D.A. Webb] was able to transfer its resistance to ‘GF305’ peach through grafting, preventing these trees from PPV infection and reducing symptomatology and viral load in PPV-infected plants. A recent study tried to identify genes responsible for this effect by studying mRNA expression through RNAseq data in peach and almond plants, before and after grafting, and before and after PPV infection. In this work, we used the same peach and almond samples, but focused the high-throughput analyses on small RNAs (sRNAs) expression. We studied massive sequencing data and found an interesting pattern of sRNAs overexpression linked to antiviral defense genes that suggested activation of these genes followed by downregulation to basal levels. We also discovered that ‘Garrigues’ almond plants were infected by different plant viruses that were transferred to peach plants. The large amounts of viral sRNAs found in grafted peaches indicated a strong RNA silencing antiviral response and led us to postulate that these plant viruses could be collaborating by cross-protection in the observed ‘Garrigues’ effect.
Project description:Spring frost is a growing risk to temperate fruit production as warmer winter conditions can lead to earlier bloom, increasing the chance of damaging cold temperatures. One strategy to minimize the impacts of frost is to breed late-flowering cultivars to avoid the frost risk period. In this study, we analyzed Late-Flowering Peach (LFP) germplasm and showed its floral buds require longer chilling and warming periods during dormancy than the control cultivar, ‘John Boy’ (JB). We identified a 983-bp deletion in an AP2 gene, dubbed euAP2a, present only in LFP but not in 14 other peach genomes analyzed. This mutation eliminates an miR172 binding site, possibly allowing the euAP2a transcript to accumulate preferentially during chilling. These findings together with an early report that a deletion in the same euAP2a causes increasing floral petals, a morphological mark that also occurs in LFP, implies that the 983-bp deletion may contribute to the late-flowering phenotype. Furthermore, RNAseq data revealed that that two chilling- and three warm-responsive co-expression modules, which were collectively composed of 2,931 genes, were differentially activated at four of 13 dormancy stages. This activation was concurrent with a transient, stage-specific down-regulation of euAP2a. However, the mutated euAP2a in LFP did not exhibit the periodic downregulation events observed in JB and the concurrent activation of the five modules, leading to potential loss of activation of two chilling-responsive modules and an 8–12-day delay of three warm-responsive modules, which corresponds to the longer chilling requirement and delayed flowering time in the LFP buds. These findings support euAP2a as a potential regulator to control both floral development and bloom time in peach. Our findings provide important insight into the mechanisms underlying flowering time in peach, as well as a novel regulatory pathway that may operate in other plants. The results provide new insights to facilitate the breeding of new cultivars with late-flowering frost-avoidance traits.
Project description:Bud dormancy is a critical developmental process for perennial plant survival, and also an important physiological phase that affects the next season’s growth of temperate fruit trees. Bud dormancy is regulated by multiple genetic factors, and affected by various environmental factors, tree age and vigor. To understand molecular mechanism of bud dormancy in Japanese apricot (Prunus mume Sieb. et Zucc.), we constructed a custom oligo DNA microarray covering the Japanese apricot dormant bud ESTs referring to peach (P. persica) genome sequence. Because endodormancy release is a chilling temperature-dependent physiological event, genes showing chilling-mediated differential expression patterns are candidates to control endodormancy release. Using the microarray constructed in this study, we monitored gene expression changes of dormant vegetative buds of Japanese apricot during prolonged artificial chilling exposure. In addition, we analyzed seasonal gene expression changes. ‘Nanko’ vegetative buds collected in November, and those exposed to chilling for 40 or 60 days were used as microarray samples. Among the 58539 different unigene probes, 2345 and 1059 genes were identified as being more than two-fold up-regulated and down-regulated, respectively, following chilling exposure for 60 days (P value < 0.05). The down-regulated genes included P. mume DORMANCY-ASSOCIATED MADS-box genes, which supported the previous quantitative RT-PCR and EST analyses showing that these genes are repressed by prolonged chilling treatments. The genes encoding lipoxygenase were remarkably up-regulated by prolonged chilling. Cluster analysis suggested that the expression of the genes showing expression changes by artificial chilling exposure were coordinately regulated by seasonal changes. Our parametric analysis of gene set enrichment suggested that genes related to jasmonic acid (JA) and oxylipin biosynthesis and metabolic processes were significantly up-regulated by prolonged chilling, whereas genes related to circadian rhythm were significantly down-regulated. The results obtained from the microarray analyses were verified by quantitative RT-PCR analysis of selected genes. Taken together, this study raised the possibility that the microarray platform constructed in this study is applicable for deeper understanding of molecular network related to agronomically important bud phisiologies including dormancy release.
Project description:Bud dormancy is a critical developmental process for perennial plant survival, and also an important physiological phase that affects the next seasonM-bM-^@M-^Ys growth of temperate fruit trees. Bud dormancy is regulated by multiple genetic factors, and affected by various environmental factors, tree age and vigor. To understand molecular mechanism of bud dormancy in Japanese apricot (Prunus mume Sieb. et Zucc.), we constructed a custom oligo DNA microarray covering the Japanese apricot dormant bud ESTs referring to peach (P. persica) genome sequence. Because endodormancy release is a chilling temperature-dependent physiological event, genes showing chilling-mediated differential expression patterns are candidates to control endodormancy release. Using the microarray constructed in this study, we monitored gene expression changes of dormant vegetative buds of Japanese apricot during prolonged artificial chilling exposure. In addition, we analyzed seasonal gene expression changes. M-bM-^@M-^XNankoM-bM-^@M-^Y vegetative buds collected in November, and those exposed to chilling for 40 or 60 days were used as microarray samples. Among the 58539 different unigene probes, 2345 and 1059 genes were identified as being more than two-fold up-regulated and down-regulated, respectively, following chilling exposure for 60 days (P value < 0.05). The down-regulated genes included P. mume DORMANCY-ASSOCIATED MADS-box genes, which supported the previous quantitative RT-PCR and EST analyses showing that these genes are repressed by prolonged chilling treatments. The genes encoding lipoxygenase were remarkably up-regulated by prolonged chilling. Cluster analysis suggested that the expression of the genes showing expression changes by artificial chilling exposure were coordinately regulated by seasonal changes. Our parametric analysis of gene set enrichment suggested that genes related to jasmonic acid (JA) and oxylipin biosynthesis and metabolic processes were significantly up-regulated by prolonged chilling, whereas genes related to circadian rhythm were significantly down-regulated. The results obtained from the microarray analyses were verified by quantitative RT-PCR analysis of selected genes. Taken together, this study raised the possibility that the microarray platform constructed in this study is applicable for deeper understanding of molecular network related to agronomically important bud phisiologies including dormancy release. In this study, we used chilling exposed bud samples (0, 40, 60 days starting at November) and seasonal monthly bud samples (June to March). For the samples in dataset 1 (three different time points during chilling treatment), three technical replicates (60K M-CM-^W 3 per sample) with three biological replicates were averaged, whereas three technical replicates were averaged for the samples in dataset 2 (10 different seasonal time points)