Function and regulation of plant ARGONAUTE proteins in response to environmental challenges: a review.

Environmental stresses diversely affect multiple processes related to the growth, development, and yield of many crops worldwide. In response, plants have developed numerous sophisticated defense mechanisms at the cellular and subcellular levels to react and adapt to biotic and abiotic stressors. RNA silencing, which is an innate immune mechanism, mediates sequence-specific gene expression regulation in higher eukaryotes. ARGONAUTE (AGO) proteins are essential components of the RNA-induced silencing complex (RISC). They bind to small noncoding RNAs (sRNAs) and target complementary RNAs, causing translational repression or triggering endonucleolytic cleavage pathways. In this review, we aim to illustrate the recently published molecular functions, regulatory mechanisms, and biological roles of AGO family proteins in model plants and cash crops, especially in the defense against diverse biotic and abiotic stresses, which could be helpful in crop improvement and stress tolerance in various plants.

Genome-wide analysis of mitogen-activated protein (MAP) kinase gene family expression in response to biotic and abiotic stresses in sugarcane.

To systematically analyze mitogen-activated protein (MAP) kinase gene families and their expression profiles in sugarcane (Saccharum spp. hybrids; Sh) under diverse biotic and abiotic stresses, we identified 15 ShMAPKs, 6 ShMAPKKs and 16 ShMAPKKKs genes in the sugarcane cultivar R570 genome. These were also confirmed in one S. spontaneum genome and two transcriptome datasets of sugarcane trigged by Acidovorax avenae subsp. avenae (Aaa) and Xanthomonas albilineans (Xa) infections. Phylogenetic analysis revealed that four subgroups were present in each ShMAPK and ShMAPKK family and three sub-families (RAF, MEKK and ZIK) presented in the ShMAPKKK family. Conserved protein motif and gene structure analyses supported the evolutionary relationships of the three families inferred from the phylogenetic analysis. All of the ShMAPK, ShMAPKK and ShMAPKKK genes identified in Saccharum spp. R570 were distributed on chromosomes 1-7 and 9-10. RNA-seq and qRT-PCR analyses indicated that ShMAPK07 and ShMAPKKK02 were defense-responsive genes in sugarcane challenged by both Aaa and Xa stimuli, while some genes were upregulated specifically by Aaa and Xa infection. Additionally, ShMAPK05 acted as a negative regulator under drought and salinity stress, but served as a positive regulator under salicylic acid (SA) treatment. ShMAPK07 plays a positive role under drought stress, but a negative role under SA treatment. ShMAPKKK01 was negatively modulated by both salinity stress and SA treatment, whereas ShMAPKKK06 was positively regulated by both of the two stress stimuli. Our results suggest that members of MAPK cascade gene families regulate adverse stress responses through multiple signal transduction pathways in sugarcane.

Transcription Factors in Plant Stress Responses: Challenges and Potential for Sugarcane Improvement.

Increasing vulnerability of crops to a wide range of abiotic and biotic stresses can have a marked influence on the growth and yield of major crops, especially sugarcane (Saccharum spp.). In response to various stresses, plants have evolved a variety of complex defense systems of signal perception and transduction networks. Transcription factors (TFs) that are activated by different pathways of signal transduction and can directly or indirectly combine with cis-acting elements to modulate the transcription efficiency of target genes, which play key regulators for crop genetic improvement. Over the past decade, significant progresses have been made in deciphering the role of plant TFs as key regulators of environmental responses in particular important cereal crops; however, a limited amount of studies have focused on sugarcane. This review summarizes the potential functions of major TF families, such as WRKY, NAC, MYB and AP2/ERF, in regulating gene expression in the response of plants to abiotic and biotic stresses, which provides important clues for the engineering of stress-tolerant cultivars in sugarcane.