Expression of genes associated with the biosynthetic pathways of abscisic acid, gibberellin, and ethylene during the germination of lettuce seeds.

Seed germination and dormancy are complex phenomena that are controlled by many genes and environmental factors. Such genes are indicated by phytohormones that interact with each other, and may cause dormancy or promote seed germination. The objective of this study was to investigate gene expression associated with the biosynthetic pathways of abscisic acid (ABA), gibberellic acid (GA), and ethylene (ET) in dormant and germinated lettuce seeds. The expressions of LsNCED, LsGA3ox1, and ACO-B were evaluated in germinating and dormant seeds from the cultivars Everglades, Babá de Verão, Verônica, Salinas, Colorado, and Regina 71. The expressions of LsNCED, LsGA3ox1, and ACO-B were related to the biosynthesis of ABA, GA, and ET, respectively; therefore, the presence of these substances depends on genotype. LsNCED expression only occurred in dormant seeds, and was connected to dormancy. LsGA3ox1expression only occurred in germinated seeds, and was connected to germination. The ACO-B gene was involved in ET biosynthesis, and was expressed differently in germinated and dormant seeds, depending on the genotype, indicating different functions for different characteristics. Furthermore, sensitivity to phytohormones appeared to be more important than the expression levels of LsNCED, LsGA3ox1, or ACO-B.

Influência alelopática de hortelã (Mentha x villosa Huds. ) sobre emergência de plântulas de alface (Lactuca sativa L. ) / Allelopathic influence of mint (Mentha x villosa Huds. ) on the emergence of lettuce (Lactuca sativa L. ) seedlings

Objetivou-se com esse trabalho avaliar a interferência de possíveis efeitos alelopáticos de Mentha x villosa Huds. sobre a emergência de Lactuca sativa L. As atividades foram conduzidas em laboratório, no Instituto de Ciências Agrárias (ICA) da Universidade Federal de Minas Gerais, em Montes Claros/MG. Foram propostos três tratamentos, sendo esses: solo A, coletado em área cultivada com hortelã no horto medicinal do ICA/UFMG; solo B, coletado em áreas adjacentes e, testemunha (papel germiteste).O delineamento experimental foi inteiramente casualizado (DIC), com sete repetições. As variáveis avaliadas foram: porcentagem e índice de velocidade de emergência. Observou-se que a emergência de plântulas de Lactuca sativa foi significativamente afetada pelo solo A (6,95 por cento) se comparada com o solo B (21,71 por cento), representando assim, uma inibição da emergência, ou seja, efeito alelopático da hortelã sobre a emergência de alface. Já o índice de velocidade de emergência (IVE) não diferiu significativamente entre os solos testados.

This study aimed to assess the interference of possible allelopathic effects of Mentha x villosa Huds. on the germination of Lactuca sativa L. The activities were carried out in laboratory, at the Institute of Agricultural Sciences (ICA) of the Federal University of Minas Gerais, Montes Claros, Minas Gerais State, Brazil. The following three treatments were proposed: soil A, collected in area cultivated with mint at the garden of ICA; soil B, collected in adjacent areas; and control (germitest paper). Experimental design was completely randomized (CR), with seven replicates. The evaluated variables were: germination percentage and speed index. The emergence of Lactuca sativa seedlings was significantly affected by soil A (6.95 percent) when compared to soil B (21.71 percent), indicating thus emergence inhibition, i.e. an allelopathic effect of mint on lettuce emergence. On the other hand, the germination speed index (GSI) did not differ significantly between the tested soils.

Suppression of SERK gene expression affects fungus tolerance and somatic embryogenesis in transgenic lettuce.

The Somatic embryogenesis receptor-like kinase (SERK) gene plays an important role in plant somatic and zygotic embryogenesis induction. The gene encodes an LRR-containing receptor-like kinase protein. Studies have been carried out focusing on different aspects of its function, but definitive conclusions on its role are far from being reached. SERK expression is generally detected in cells in which somatic or zygotic embryogenesis has been triggered. Transgenic lettuce lines were produced to silence the endogenous SERK gene using antisense RNA. The average number of seeds per flower in the R(1) and R(2) generations was similar for both transgenic and non-transgenic lines. However, a reduction in the number of viable grained seeds was observed in four studied transgenic lines. Endogenous SERK expression analysis revealed the absence of detectable LsSERK gene transcripts in three transgenic lines, which presented a reduction in their ability to form in vitro somatic embryonic structures. In addition, transgenic lines showed enhanced susceptibility to the pathogenic fungus Sclerotinia sclerotiorum, when compared to control plants. The results support the idea that SERK genes might not only be involved in plant growth and development, but probably also in a general mechanism of biotic and abiotic stress perception.