Agricultural systems are currently facing significant issues, primarily due to population growth rates in the context of global climate change. Rising temperatures cause plant heat stress and impact ...crop yield, which in turn compromises global food production and safety. Climate change is also having a significant impact on water availability around the world, and droughts are becoming more frequent and severe in many regions. The combined effect of both heat and drought stresses increases plant damage, resulting in reduced plant development and productivity loss. Therefore, developing heat–drought-tolerant crop varieties is crucial for enhancing yield under these challenging conditions. Tomato (Solanum lycopersicum L.), a major vegetable crop highly appreciated for its nutritional qualities, is particularly sensitive to extreme temperatures, which have a significant negative impact on tomato fruit setting and cause male gametophyte abortion. In this work, a classical genetic approach was employed to identify tomato genotypes showing a resilient response to combined heat and drought stress conditions. A phenotype screening of a natural germplasm collection and an ethyl methanesulfonate (EMS) mutagenized population resulted in the identification of a significant number of tomato lines tolerant to combined heat and drought conditions, specifically 161 EMS lines and 24 natural accessions as tolerant. In addition, TILLING and Eco-TILLING analyses were used as proof-of-concept to isolate new genetic variants of genes previously reported as key regulators of abiotic stress responses in different species. The identification of these variants holds the potential to provide suitable plant material for breeding programs focused on enhancing tomato resilience to adverse climate conditions.
Tomato (Solanum lycopersicum L.) is a major horticultural crop and a model species among eudicots, especially for traits related to reproductive development. Although considerable progress has been ...made since the tomato genome sequence project was completed, most of the genes identified remain predictions with an unknown or hypothetical function. This lack of functional characterization hampers the use of the huge amount of genomic information available to improve the quality and productivity of this crop. Reverse genetics strategies such as artificial mutagenesis and next-generation sequencing approaches build the perfect tandem for increasing knowledge on functional annotation of tomato genes. This work reports the phenotypic characterization of a tomato mutant collection generated from an EMS chemical mutagenesis program aimed to identify interesting agronomic mutants and novel gene functions. Tomato mutants were grouped into fourteen phenotypic classes, including vegetative and reproductive development traits, and the inheritance pattern of the identified mutations was studied. In addition, causal mutation of a selected mutant line was isolated through a mapping-by-sequencing approach as a proof of concept of this strategy’s successful implementation. Results support tomato mutagenesis as an essential tool for functional genomics in this fleshy-fruited model species and a highly valuable resource for future breeding programs of this crop species aimed at the development of more productive and resilient new varieties under challenging climatic and production scenarios.
Ca
is a second messenger that mediates plant responses to abiotic stress; Ca
signals need to be decoded by Ca
sensors that translate the signal into physiological, metabolic, and molecular responses. ...Recent research regarding the Ca
sensor CALCINEURIN B-LIKE PROTEIN 10 (CBL10) has resulted in important advances in understanding the function of this signaling component during abiotic stress tolerance. Under saline conditions, CBL10 function was initially understood to be linked to regulation of Na
homeostasis, protecting plant shoots from salt stress. During this process, CBL10 interacts with the CBL-interacting protein kinase 24 (CIPK24, SOS2), this interaction being localized at both the plasma and vacuolar (tonoplast) membranes. Interestingly, recent studies have exposed that CBL10 is a regulator not only of Na
homeostasis but also of Ca
under salt stress, regulating Ca
fluxes in vacuoles, and also at the plasma membrane. This review summarizes new research regarding functions of CBL10 in plant stress tolerance, predominantly salt stress, as this is the most commonly studied abiotic stress associated with the function of this regulator. Special focus has been placed on some aspects that are still unclear. We also pay particular attention on the proven versatility of CBL10 to activate (in a CIPK-dependent manner) or repress (by direct interaction) downstream targets, in different subcellular locations. These in turn appear to be the link through which CBL10 could be a key master regulator of stress signaling in plants and also a crucial participant in fruit development and quality, as disruption of
results in inadequate Ca
partitioning in plants and fruit. New emerging roles associated with other abiotic stresses in addition to salt stress, such as drought, flooding, and K
deficiency, are also addressed in this review. Finally, we provide an outline of recent advances in identification of potential targets of CBL10, as CBL10/CIPKs complexes and as CBL10 direct interactions. The aim is to showcase new research regarding this master regulator of abiotic stress tolerance that may be essential to the maintenance of crop productivity under abiotic stress. This is particularly pertinent when considering the scenario of a projected increase in extreme environmental conditions due to climate change.
Abstract
Pollen development is a crucial biological process indispensable for seed set in flowering plants and for successful crop breeding. However, little is known about the molecular mechanisms ...regulating pollen development in crop species. This study reports a novel male-sterile tomato mutant, pollen deficient 2 (pod2), characterized by the production of non-viable pollen grains and resulting in the development of small parthenocarpic fruits. A combined strategy of mapping-by-sequencing and RNA interference-mediated gene silencing was used to prove that the pod2 phenotype is caused by the loss of Solanum lycopersicum G-type lectin receptor kinase II.9 (SlG-LecRK-II.9) activity. In situ hybridization of floral buds showed that POD2/SlG-LecRK-II.9 is specifically expressed in tapetal cells and microspores at the late tetrad stage. Accordingly, abnormalities in meiosis and tapetum programmed cell death in pod2 occurred during microsporogenesis, resulting in the formation of four dysfunctional microspores leading to an aberrant microgametogenesis process. RNA-seq analyses supported the existence of alterations at the final stage of microsporogenesis, since we found tomato deregulated genes whose counterparts in Arabidopsis are essential for the normal progression of male meiosis and cytokinesis. Collectively, our results revealed the essential role of POD2/SlG-LecRK-II.9 in regulating tomato pollen development.
POD2encodes a tomato G-type lectin receptor kinase vital for functional pollen formation. The loss of POD2function impairs meiosis and tapetum degradation, resulting in male sterility and parthenocarpy.
•Tomato mutants impaired in adventitious organogenesis were identified.•The genes altered in these mutants are key regulators of adventitious organogenesis.•Gene altered in tdc-1 plays a specific ...role in callus growth.•Gene altered in tds-1 plays a specific role in adventitious shoot development.•SlMAPKKK17 gene plays an important role in adventitious shoot-bud differentiation.
The screening of 862 T-DNA lines was carried out to approach the genetic dissection of indirect adventitious organogenesis in tomato. Several mutants defective in different phases of adventitious organogenesis, namely callus growth (tdc-1), bud differentiation (tdb-1, -2, -3) and shoot-bud development (tds-1) were identified and characterized. The alteration of the TDC-1 gene blocked callus proliferation depending on the composition of growth regulators in the culture medium. Calli from tds-1 explants differentiated buds but did not develop normal shoots. Histological analysis showed that their abnormal development is due to failure in the organization of normal adventitious shoot meristems. Interestingly, tdc-1 and tds-1 mutant plants were indistinguishable from WT ones, indicating that the respective altered genes play specific roles in cell proliferation from explant cut zones (TDC-1 gene) or in the organization of adventitious shoot meristems (TDS-1 gene). Unlike the previous, plants of the three mutants defective in the differentiation of adventitious shoot-buds (tdb-1, -2, -3) showed multiple changes in vegetative and reproductive traits. Cosegregation analyses revealed the existence of an association between the phenotype of the tdb-3 mutant and a T-DNA insert, which led to the discovery that the SlMAPKKK17 gene is involved in the shoot-bud differentiation process.
Abstract Flower development is a crucial step towards the completion of the plant life cycle. Physiological processes and gene regulatory mechanisms underlying flower formation have been extensively ...characterized, and the implication of MADS-box transcription factors as primary regulators of flower morphology has been widely described, mainly due to the analysis of loss-of-function mutants in model species. Nevertheless, detailed characterization of allele variation in several MADS-box homologous genes from crop species remains undescribed. Here, we have characterized a tomato mutant with aberrant flower development. Mutant plants exhibit changes in petal cell identity, as well as homeotic transformations of stamens into carpelloid structures, which in most cases result in succulent organs. Molecular analysis proved that a loss-of-function mutation in the TOMATO MADS-BOX 6 (TM6) gene is responsible for this mutant phenotype. Furthermore, as a result of the loss of function of TM6, misregulation of the transcription and mRNA processing of other MADS-box genes involved in reproductive development has been detected. Our findings demonstrate that TM6 is a key player in the complex regulatory network of MADS-box genes controlling flower development and also provide a novel mutant that may be useful for generating male sterile lines in tomatoes.
Characterization of a new tomato (
) T-DNA mutant allowed for the isolation of the
(
) gene whose lack of function was responsible for the severe alterations observed in the shoot apex and ...reproductive organs under salinity conditions. Physiological studies proved that
gene is required to maintain a proper low Na
/Ca
ratio in growing tissues allowing tomato growth under salt stress. Expression analysis of the main responsible genes for Na
compartmentalization (i.e.
,
,
,
and V-ATPase
) supported a reduced capacity to accumulate Na
in
mutant leaves, which resulted in a lower uploading of Na
from xylem, allowing the toxic ion to reach apex and flowers. Likewise, the tomato
and
(
), key genes for Ca
fluxes to the vacuole, showed abnormal expression in
plants indicating an impaired Ca
release from vacuole. Additionally, complementation assay revealed that
is a true ortholog of the Arabidopsis (
)
gene, supporting that the essential function of CBL10 is conserved in Arabidopsis and tomato. Together, the findings obtained in this study provide new insights into the function of
in salt stress tolerance. Thus, it is proposed that SlCBL10 mediates salt tolerance by regulating Na
and Ca
fluxes in the vacuole, cooperating with the vacuolar cation channel
and the two vacuolar H
-pumps,
and
, which in turn are revealed as potential targets of
.
Tomato CALCINEURIN B-LIKE PROTEIN 10 (SlCBL10) ensures plant growth by regulating proper distribution of Na+ and Ca2+ in the shoot apical meristem and developing organs under salt stress.
...Characterization of a new tomato (
Solanum lycopersicum
) T-DNA mutant allowed for the isolation of the
CALCINEURIN B-LIKE PROTEIN 10
(
SlCBL10
) gene whose lack of function was responsible for the severe alterations observed in the shoot apex and reproductive organs under salinity conditions. Physiological studies proved that
SlCBL10
gene is required to maintain a proper low Na
+
/Ca
2+
ratio in growing tissues allowing tomato growth under salt stress. Expression analysis of the main responsible genes for Na
+
compartmentalization (i.e.
Na
+
/H
+
EXCHANGERs
,
SALT OVERLY SENSITIVE
,
HIGH-AFFINITY K+ TRANSPORTER 1;2
,
H
+
-pyrophosphatase AVP1
SlAVP1
and V-ATPase
SlVHA-A1
) supported a reduced capacity to accumulate Na
+
in
Slcbl10
mutant leaves, which resulted in a lower uploading of Na
+
from xylem, allowing the toxic ion to reach apex and flowers. Likewise, the tomato
CATION EXCHANGER 1
and
TWO-PORE CHANNEL 1
(
SlTPC1
), key genes for Ca
2+
fluxes to the vacuole, showed abnormal expression in
Slcbl10
plants indicating an impaired Ca
2+
release from vacuole. Additionally, complementation assay revealed that
SlCBL10
is a true ortholog of the Arabidopsis (
Arabidopsis thaliana
)
CBL10
gene, supporting that the essential function of CBL10 is conserved in Arabidopsis and tomato. Together, the findings obtained in this study provide new insights into the function of
SlCBL10
in salt stress tolerance. Thus, it is proposed that SlCBL10 mediates salt tolerance by regulating Na
+
and Ca
2+
fluxes in the vacuole, cooperating with the vacuolar cation channel
SlTPC1
and the two vacuolar H
+
-pumps,
SlAVP1
and
SlVHA-A1
, which in turn are revealed as potential targets of
SlCBL10
.
To the editor, We have read with interest the article published in Arthritis Research & Therapy by Kushimoto et al. suggesting that the HLA-B*52 allele may indicate the presence of diffuse ...extracranial large vessel vasculitis (LVV) in patients with giant cell arteritis (GCA) 1. Different studies point to the influence of genes located in the MHC region, in particular the HLA-DRB1*04 alleles 7. Since the pattern of vascular involvement in Takayasu arteritis often resembles that found in patients with extracranial GCA, and the genetic contribution to the pathogenesis of the disease is mainly mediated by the HLA-B*52 allele 8, we wondered if in Caucasian individuals the association of HLA with GCA may differ according to the predominant pattern of the disease. ...HLA-B*52 cannot be considered as a marker for extracranial LVV in Caucasian individuals over 50 years of age.
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