Biology subjects

Jernstedt, J.

Publications and source records attributed to Jernstedt, J..

5 recordsLinked to original sources

bioRxiv2025

Key molecular and cellular events of table olive fruit abscission zone formation during natural maturation and after ethephon treatment

Abscission zones are specialized cell layers that enable organ detachment, yet their morphology and regulation vary among species. Olive (Olea europaea), a non-climacteric fruit, requires high concentrations of ethylene-releasing compounds to reduce fruit removal force (FRF) for mechanical harvest. To elucidate mechanisms of fruit abscission zone (FAZ) development in olive, we integrated physiological, transcriptomic, and cellular analyses during natural maturation and after ethephon treatment. Olive fruits emitted low ethylene at color transition, coinciding with declining FRF, and application of 1500 ppm ethephon reduced FRF after one week. Transcriptome analyses of FAZ tissues, using a mesocarp-subtraction strategy to isolate FAZ-specific responses, identified 733 FAZ-specific genes shared between natural maturation and ethephon treatments, including genes of {beta}-1,3-glucanases, pectate lyases, and the phenylpropanoid pathway. Microscopy revealed lignification and alkalization of FAZ, accompanied by reduced low-methylesterified homogalacturonan and non-fucosylated xyloglucan. Increased glucanase activity and reduction in plasmodesmata callose likely facilitate cellular communication during abscission. Further, this study provides the first evidence of FAZ alkalization and implicates transporter upregulation in pH regulation preceding abscission. Our findings advance understanding of abscission biology in non-climacteric fruits and delineate conserved features of FAZ development. Summary StatementIntegrated physiological, transcriptomic, and cellular analyses reveal that fruit abscission zone development in olive involves lignification, alkalization, and coordinated cell wall remodeling, identifying {beta}-1,3-glucanases, pH-regulating transporters, and pectate lyases that facilitate cell separation in a non-climacteric fruit.

plant biology↗

bioRxiv2023

Difference in Kernel Shape and Endocarp Anatomy Promote Dehiscence in Pistachio Endocarp

A fully split shell in pistachio (Pistacia vera) is a trait that is preferred by consumers and is a criterion in evaluating the grade of the pistachio nut. However, while the expanding kernel has been hypothesized to provide the physical force needed for shell split, the mechanisms that control shell split remains unknown. Furthermore, it is intriguing how the shell, or endocarp, splits at the suture ridge when there is no clear dehiscence zone. The objectives of this study were to 1) identify traits associated with dehiscence in fruit in the high split rate cultivar Golden Hills when compared to the lower split rate cultivar Kerman and determine the anatomical features associated with endocarp dehiscence at the suture region, and 2) examine the effect of kernel shape on endocarp dehiscence. We determined that despite of the fact that the pistachio endocarp is primarily composed of a single type of polylobate schlerenchyma cell, specialization of cell shape and size at the suture site results in smaller, more flattened cells. We report that there is a furrowing of the shell at the dorsal and apical suture site, where dehiscence initiates. This furrowing is not observed at the ventral suture site or in the indehiscent fruit of Pistacia atlantica, a species that has been used as rootstock for P. vera. In addition, the size of the kernel in the sagittal axis (the width) is strongly associated with higher split rate. Based on our results, a tentative model emerges where, in the absence of specialized cell types, cell shape modification can create an anatomically distinct region that is mechanically weak in the endocarp for the initiation of dehiscence, while the force from the width of the kernel is necessary for the shell split rate difference as observed in cultivars.

plant biology↗

bioRxiv2022

Loss of pod strings in common bean is associated with gene duplication, retrotransposon insertion, and overexpression of PvIND

Regulation of fruit development has been central in the evolution and domestication of flowering plants. In common bean (Phaseolus vulgaris L.), a major global staple crop, the two main economic categories are distinguished by differences in fiber deposition in pods: a) dry beans with fibrous and stringy pods; and b) stringless snap/green beans with reduced fiber deposition, but which frequently revert to the ancestral stringy state. To better understand control of this important trait, we first characterized developmental patterns of gene expression in four phenotypically diverse varieties. Then, using isogenic stringless/revertant pairs of six snap bean varieties, we identified strong overexpression of the common bean ortholog of INDEHISCENT (PvIND) in non-stringy types compared to their string-producing counterparts. Microscopy of these pairs indicates that PvIND overexpression is associated with overspecification of weak dehiscence zone cells throughout the entire pod vascular sheath. No differences in PvIND DNA methylation were correlated with pod string phenotype. Sequencing of a 500 kb region surrounding PvIND in the stringless snap bean cultivar Hystyle revealed that PvIND had been duplicated into two tandem repeats, and that a Ty1-copia retrotransposon was inserted between these tandem repeats, possibly driving PvIND overexpression. Further sequencing of stringless/revertant isogenic pairs and diverse materials indicated that these sequence features had been uniformly lost in revertant types and were strongly predictive of pod phenotype, supporting their role in PvIND overexpression and pod string phenotype. SignificanceFruit dehiscence is a key trait for seed dissemination. In legumes, e.g., common bean, dehiscence relies on the presence of fibers, including pod "strings". Selections during domestication and improvement have decreased (dry beans) or eliminated (snap beans) fibers, but reversion to the fibrous state occurs frequently in snap beans. In this article, we document that fiber loss or gain is controlled by structural changes at the PvIND locus, a homolog of the Arabidopsis INDEHISCENT gene. These changes include a duplication of the locus and insertion/deletion of a retrotransposon, which are associated with significant changes in PvIND expression. Our findings shed light on the molecular basis of unstable mutations and provide potential solutions to an important pod quality issue. Competing Interest StatementThe authors have no competing interests.

plant biology↗

bioRxiv2019

Genetic control of pod dehiscence in domesticatedcommon bean: Associations with range expansionand local aridity conditions

SignificancePlant domestication has radically modified crop morphology and development. Nevertheless, many crops continue to display some atavistic characteristics that were advantageous to their wild ancestors, such as pod dehiscence (PD). Domesticated common bean (Phaseolus vulgaris), a nutritional staple for millions of people globally, shows considerable variation in PD. Here, we identified multiple genetic regions controlling PD in common bean grown throughout geographically distributed lineages. For example, on chromosome Pv03, PvPdh1 shows a single base-pair substitution that is strongly associated with decreased PD and expansion of the crop into northern Mexico, where the arid conditions promote PD. The environmental dependency and genetic redundancy explain the maintenance of atavistic traits under domestication. Knowledge of PD genetics will assist in developing aridity-adapted varieties.\n\nAbstractA reduction in pod dehiscence (PD) is an important part of the domestication syndrome in legumes, including common bean. Despite this, many modern dry bean varieties continue to suffer yield reductions due to dehiscence, an atavistic trait, which is particularly problematic in hot, dry environments. To date, the genetic control of this important trait has been only partially resolved. Using QTL mapping and GWAS, we identified major PD QTLs in dry beans on chromosomes Pv03, Pv05, Pv08, and Pv09, three of which had not been described previously. We further determined that the QTL on chromosome Pv03, which is strongly associated with PD in Middle American beans, includes a dirigent-like candidate gene orthologous to Pod dehiscence 1 (Pdh1) of soybean. In this gene, we identified a substitution in a highly conserved amino acid that is unique to PD-resistant varieties. This allele is associated with the expansion of Middle American domesticated common beans into the arid environments of northern Mexico, resulting in a high allelic frequency in the domesticated ecogeographic race Durango. The polygenic redundancy and environmental dependency of PD resistance may explain the maintenance of this atavistic characteristic after domestication. Use of these alleles in breeding will reduce yield losses in arid growing conditions, which are predicted to become more widespread in coming decades.

plant biology↗

bioRxiv2019

Wheat VRN1 and FUL2 play critical and redundant roles in spikelet meristem identity and spike determinacy

The spikelet is the basic unit of the grass inflorescence. In this study, we show that wheat MADS-box genes VRN1, FUL2 and FUL3 play critical and redundant roles in spikelet and spike development, and also affect flowering time and plant height. In the vrn1ful2ful3-null triple mutant, the inflorescence meristem formed a normal double-ridge structure, but then the lateral meristems generated vegetative tillers subtended by leaves instead of spikelets. These results suggest an essential role of these three genes in the determination of spikelet meristem identity and the suppression of the lower ridge. Inflorescence meristems of vrn1ful2ful3-null and vrn1ful2-null remained indeterminate and single vrn1-null and ful2-null mutants showed delayed formation of the terminal spikelet and increased number of spikelets per spike. Moreover, the ful2-null mutant showed more florets per spikelet, which together with a higher number of spikelets, resulted in a significant increase in the number of grains per spike in the field. Our results suggest that a better understanding of the mechanisms underlying wheat spikelet and spike development can inform future strategies to improve grain yield in wheat.\n\nSUMMARY STATEMENTThe wheat MADS-box proteins VRN1, FUL2 and FUL3 play critical and overlapping roles in the development of spikelets, which are the basic unit of all grass inflorescences.

developmental biology↗