BackgroundThe SR/CAMTA proteins represent a small family of transcription activators that play important roles in plant responses to biotic and abiotic stresses. Seven SlSR/CAMTA genes were identified in tomato as tomato counterparts of SR/CAMTA; however, the involvement of SlSRs/CAMTAs in biotic and abiotic stress responses is not clear. In this study, we performed functional analysis of the SlSR/CAMTA family for their possible functions in defense response against pathogens and tolerance to drought stress.ResultsExpression of SlSRs was induced with distinct patterns by Botrytis cinerea and Pseudomonas syringae pv. tomato (Pst) DC3000. Virus-induced gene silencing (VIGS)-based knockdown of either SlSR1 or SlSR3L in tomato resulted in enhanced resistance to B. cinerea and Pst DC3000 and led to constitutive accumulation of H2O2, elevated expression of defense genes, marker genes for pathogen-associated molecular pattern-triggered immunity, and regulatory genes involved in the salicylic acid- and ethylene-mediated signaling pathways. Furthermore, the expression of SlSR1L and SlSR2L in detached leaves and whole plants was significantly induced by drought stress. Silencing of SlSR1L led to decreased drought stress tolerance, accelerated water loss in leaves, reduced root biomass and attenuated expression of drought stress responsive genes in tomato. The SlSR1 and SlSR3L proteins were localized in the nucleus of plant cells when transiently expressed in Nicotiana benthamiana and had transcriptional activation activity in yeast.ConclusionsVIGS-based functional analyses demonstrate that both SlSR1 and SlSR3L in the tomato SlSR/CAMTA family are negative regulators of defense response against B. cinerea and Pst DC3000 while SlSR1L is a positive regulator of drought stress tolerance in tomato.

BackgroundMitogen-activated protein kinase (MAPK) cascades are highly conserved signaling modules that mediate the transduction of extracellular stimuli via receptors/sensors into intracellular responses and play key roles in plant immunity against pathogen attack. However, the function of tomato MAPK kinases, SlMKKs, in resistance against Botrytis cinerea remains unclear yet.ResultsA total of five SlMKK genes with one new member, SlMKK5, were identified in tomato. qRT-PCR analyses revealed that expression of SlMKK2 and SlMKK4 was strongly induced by B. cinerea and by jasmonic acid and ethylene precursor 1-amino cyclopropane-1-carboxylic acid. Virus-induced gene silencing (VIGS)-based knockdown of individual SlMKKs and disease assays identified that SlMKK2 and SlMKK4 but not other three SlMKKs (SlMKK1, SlMKK3 and SlMKK5) are involved in resistance against B. cinerea. Silencing of SlMKK2 or SlMKK4 resulted in reduced resistance to B. cinerea, increased accumulation of reactive oxygen species and attenuated expression of defense genes after infection of B. cinerea in tomato plants. Furthermore, transient expression of constitutively active phosphomimicking forms SlMKK2DD and SlMKK4DD in leaves of Nicotiana benthamiana plants led to enhanced resistance to B. cinerea and elevated expression of defense genes.ConclusionsVIGS-based knockdown of SlMKK2 and SlMKK4 expression in tomato and gain-of-function transient expression of constitutively active phosphomimicking forms SlMKK2DD and SlMKK2DD in N. benthamiana demonstrate that both SlMKK2 and SlMKK4 function as positive regulators of defense response against B. cinerea.

BackgroundThe SR/CAMTA proteins represent a small family of transcription activators that play important roles in plant responses to biotic and abiotic stresses. Seven SlSR/CAMTA genes were identified in tomato as tomato counterparts of SR/CAMTA; however, the involvement of SlSRs/CAMTAs in biotic and abiotic stress responses is not clear. In this study, we performed functional analysis of the SlSR/CAMTA family for their possible functions in defense response against pathogens and tolerance to drought stress.ResultsExpression of SlSRs was induced with distinct patterns by Botrytis cinerea and Pseudomonas syringae pv. tomato (Pst) DC3000. Virus-induced gene silencing (VIGS)-based knockdown of either SlSR1 or SlSR3L in tomato resulted in enhanced resistance to B. cinerea and Pst DC3000 and led to constitutive accumulation of H2O2, elevated expression of defense genes, marker genes for pathogen-associated molecular pattern-triggered immunity, and regulatory genes involved in the salicylic acid- and ethylene-mediated signaling pathways. Furthermore, the expression of SlSR1L and SlSR2L in detached leaves and whole plants was significantly induced by drought stress. Silencing of SlSR1L led to decreased drought stress tolerance, accelerated water loss in leaves, reduced root biomass and attenuated expression of drought stress responsive genes in tomato. The SlSR1 and SlSR3L proteins were localized in the nucleus of plant cells when transiently expressed in Nicotiana benthamiana and had transcriptional activation activity in yeast.ConclusionsVIGS-based functional analyses demonstrate that both SlSR1 and SlSR3L in the tomato SlSR/CAMTA family are negative regulators of defense response against B. cinerea and Pst DC3000 while SlSR1L is a positive regulator of drought stress tolerance in tomato.

BackgroundMitogen-activated protein kinase (MAPK) cascades are highly conserved signaling modules that mediate the transduction of extracellular stimuli via receptors/sensors into intracellular responses and play key roles in plant immunity against pathogen attack. However, the function of tomato MAPK kinases, SlMKKs, in resistance against Botrytis cinerea remains unclear yet.ResultsA total of five SlMKK genes with one new member, SlMKK5, were identified in tomato. qRT-PCR analyses revealed that expression of SlMKK2 and SlMKK4 was strongly induced by B. cinerea and by jasmonic acid and ethylene precursor 1-amino cyclopropane-1-carboxylic acid. Virus-induced gene silencing (VIGS)-based knockdown of individual SlMKKs and disease assays identified that SlMKK2 and SlMKK4 but not other three SlMKKs (SlMKK1, SlMKK3 and SlMKK5) are involved in resistance against B. cinerea. Silencing of SlMKK2 or SlMKK4 resulted in reduced resistance to B. cinerea, increased accumulation of reactive oxygen species and attenuated expression of defense genes after infection of B. cinerea in tomato plants. Furthermore, transient expression of constitutively active phosphomimicking forms SlMKK2DD and SlMKK4DD in leaves of Nicotiana benthamiana plants led to enhanced resistance to B. cinerea and elevated expression of defense genes.ConclusionsVIGS-based knockdown of SlMKK2 and SlMKK4 expression in tomato and gain-of-function transient expression of constitutively active phosphomimicking forms SlMKK2DD and SlMKK2DD in N. benthamiana demonstrate that both SlMKK2 and SlMKK4 function as positive regulators of defense response against B. cinerea.

BackgroundThe shape of grass leaves possesses great value in both agronomy and developmental biology research. Leaf rolling is one of the important traits in rice (Oryza sativa L.) breeding. MYB transcription factors are one of the largest gene families and have important roles in plant development, metabolism and stress responses. However, little is known about their functions in rice.ResultsIn this study, we report the functional characterization of a rice gene, OsMYB103L, which encodes an R2R3-MYB transcription factor. OsMYB103L was localized in the nucleus with transactivation activity. Overexpression of OsMYB103L in rice resulted in a rolled leaf phenotype. Further analyses showed that expression levels of several cellulose synthase genes (CESAs) were significantly increased, as was the cellulose content in OsMYB103L overexpressing lines. Knockdown of OsMYB103L by RNA interference led to a decreased level of cellulose content and reduced mechanical strength in leaves. Meanwhile, the expression levels of several CESA genes were decreased in these knockdown lines.ConclusionsThese findings suggest that OsMYB103L may target CESA genes for regulation of cellulose synthesis and could potentially be engineered for desirable leaf shape and mechanical strength in rice.

BackgroundThe shape of grass leaves possesses great value in both agronomy and developmental biology research. Leaf rolling is one of the important traits in rice (Oryza sativa L.) breeding. MYB transcription factors are one of the largest gene families and have important roles in plant development, metabolism and stress responses. However, little is known about their functions in rice.ResultsIn this study, we report the functional characterization of a rice gene, OsMYB103L, which encodes an R2R3-MYB transcription factor. OsMYB103L was localized in the nucleus with transactivation activity. Overexpression of OsMYB103L in rice resulted in a rolled leaf phenotype. Further analyses showed that expression levels of several cellulose synthase genes (CESAs) were significantly increased, as was the cellulose content in OsMYB103L overexpressing lines. Knockdown of OsMYB103L by RNA interference led to a decreased level of cellulose content and reduced mechanical strength in leaves. Meanwhile, the expression levels of several CESA genes were decreased in these knockdown lines.ConclusionsThese findings suggest that OsMYB103L may target CESA genes for regulation of cellulose synthesis and could potentially be engineered for desirable leaf shape and mechanical strength in rice.