Dinâmica evolutiva de Cucurbita argyosperma do centro mesoamericano de domesticação por meio de marcadores moleculares SSR

The objective of this work was to evaluate the evolutionary dynamics of the wild-weedy-domestic gene pool of Cucurbita argyrosperma squash by estimating the levels of genetic diversity and gene flow in the putative area of its domestication. Nine populations were collected, and DNA was extracted from young leaves harvested separately from approximately 20 individuals in each population. The DNA fragments were amplified with eight pairs of SSR primers and separated by electrophoresis in 5% denaturing polyacrylamide gels. Genetic diversity and the amount of gene flow were estimated in the populations, and Bayesian grouping was used to determine the levels of gene infiltration and probability of ancestry. The ethnobotanical exploration indicated that the evolutionary dynamics in the area occurred under five different ecological scenarios. Eighty-seven alleles with 75% to 100% polymorphic loci were identified. The greater genetic diversity in the weedy-domestic populations may have been the product of recombination due to the high gene flow between these populations promoted by pollinators and human selection. There is high gene flow between the wild and cultivated populations of C. argyrosperma in its domestication centre, highlighting the importance of conserving and maintaining these genetic resources. O objetivo deste trabalho foi avaliar a dinâmica evolutiva do pool genético silvestre-arvense-doméstico da abóbora (Cucurbita argyrosperma) ao estimar os níveis de diversidade genética e o fluxo gênico em sua provável área domesticação. Foram coletadas nove populações, tendo-se extraído o DNA de folhas jovens de cerca de 20 plantas de cada população. Os fragmentos de DNA foram amplificados por meio de oito pares de iniciadores de sequência simples repetida (SSR) e separados por eletroforese em 5% de gel de desnaturação de poliacrilamida. Estimaram-se a diversidade genética e o fluxo gênico para as populações, e utilizou-se o agrupamento bayesiano para determinar os níveis de infiltração gênica e probabilidade de ancestralidade. A investigação etnobotânica mostrou que a dinâmica evolutiva na área ocorreu em cinco cenários ecológicos diferentes. Foram identificados 87 alelos com 75 e 100% de loci polimórficos. A maior diversidade genética nas populações arvense-domésticas pode ter sido resultante da recombinação devido ao alto fluxo gênico entre estas populações, ocasionado pelos polinizadores e pela seleção humana. Há grande fluxo gênico entre as populações silvestres e cultivadas de C. argyrosperma no centro de domesticação, o que indica a importância da conservação e da manutenção destes recursos genéticos

The Banana MaWRKY18, MaWRKY45, MaWRKY60 and MaWRKY70 Genes Encode Functional Transcription Factors and Display Differential Expression in Response to Defense Phytohormones

WRKY transcription factors (TFs) play key roles in plant defense responses through phytohormone signaling pathways. However, their functions in tropical fruit crops, especially in banana, remain largely unknown. Several WRKY genes from the model plants rice (OsWRKY45) and Arabidopsis (AtWRKY18, AtWRKY60, AtWRKY70) have shown to be attractive TFs for engineering disease resistance. In this study, we isolated four banana cDNAs (MaWRKY18, MaWRKY45, MaWRKY60, and MaWRKY70) with homology to these rice and ArabidopsisWRKY genes. The MaWRKY cDNAs were isolated from the wild banana Musa acuminata ssp. malaccensis, which is resistant to several diseases of this crop and is a progenitor of most banana cultivars. The deduced amino acid sequences of the four MaWRKY cDNAs revealed the presence of the conserved WRKY domain of ~60 amino acids and a zinc-finger motif at the N-terminus. Based on the number of WRKY repeats and the structure of the zinc-finger motif, MaWRKY18 and MaWRKY60 belong to group II of WRKY TFs, while MaWRKY45 and MaWRKY70 are members of group III. Their corresponding proteins were located in the nuclei of onion epidermal cells and were shown to be functional TFs in yeast cells. Moreover, expression analyses revealed that the majority of these MaWRKY genes were upregulated by salicylic acid (SA) or methyl jasmonate (MeJA) phytohormones, although the expression levels were relatively higher with MeJA treatment. The fact that most of these banana WRKY genes were upregulated by SA or MeJA, which are involved in systemic acquired resistance (SAR) or induced systemic resistance (ISR), respectively, make them interesting candidates for bioengineering broad-spectrum resistance in this crop