Pathogens hitting the plant cell wall is the first impetus that triggers the phenylpropanoid pathway for plant defense. The phenylpropanoid pathway bifurcates into the production of an enormous array of compounds based on the few intermediates of the shikimate pathway in response to cell wall breaches by pathogens. The whole metabolomic pathway is a complex network regulated by multiple gene families and it exhibits refined regulatory mechanisms at the transcriptional, post-transcriptional, and post-translational levels. The pathway genes are involved in the production of anti-microbial compounds as well as signaling molecules. The engineering in the metabolic pathway has led to a new plant defense system of which various mechanisms have been proposed including salicylic acid and antimicrobial mediated compounds. In recent years, some key players like phenylalanine ammonia lyases (PALs) from the phenylpropanoid pathway are proposed to have broad spectrum disease resistance (BSR) without yield penalties. Now we have more evidence than ever, yet little understanding about the pathway-based genes that orchestrate rapid, coordinated induction of phenylpropanoid defenses in response to microbial attack. It is not astonishing that mutants of pathway regulator genes can show conflicting results. Therefore, precise engineering of the pathway is an interesting strategy to aim at profitably tailored plants. Here, this review portrays the current progress and challenges for phenylpropanoid pathway-based resistance from the current prospective to provide a deeper understanding.

Members of the plant-specific GASA (gibberellic acid-stimulated Arabidopsis) gene family have multiple potential roles in plant growth and development, particularly in flower induction and seed development. However, limited information is available about the functions of these genes in fruit plants, particularly in grapes. We identified 14 GASA genes in grapevine (Vitis vinifera L.) and performed comprehensive bioinformatics and expression analyses. In the bioinformatics analysis, the locations of genes on chromosomes, physiochemical properties of proteins, protein structure, and subcellular positions were described. We evaluated GASA proteins in terms of domain structure, exon-intron distribution, motif arrangements, promoter analysis, phylogenetic, and evolutionary history. According to the results, the GASA domain is conserved in all proteins and the proteins are divided into three well-conserved subgroups. Synteny analysis proposed that segmental and tandem duplication have played a role in the expansion of the GASA gene family in grapes, and duplicated gene pairs have negative selection pressure. Most of the proteins were predicted to be in the extracellular region, chloroplasts, and the vacuole. In silico promoter analysis suggested that the GASA genes may influence different hormone signaling pathways and stress-related mechanisms. Additionally, we performed a comparison of the expression between seedless (Thompson seedless) and seeded (Red globe) cultivars in different plant parts, including the ovule during different stages of development. Furthermore, some genes were differentially expressed in different tissues, signifying their role in grapevine growth and development. Several genes (VvGASA2 and 7) showed different expression levels in later phases of seed development in Red globe and Thompson seedless, suggesting their involvement in seed development. Our study presents the first genome-wide identification and expression profiling of grapevine GASA genes and provides the basis for functional characterization of GASA genes in grapes. We surmise that this information may provide new potential resources for the molecular breeding of grapes.

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