Muhammad Arshad

The studies on the prevalence and genetic diversity of begomoviruses in Saudi Arabia are minimal. In this study, field-grown symptomatic tomato and muskmelon plants were collected, and initially, begomovirus infection was confirmed by the core coat protein sequences. Four tomato and two muskmelon plants with viral infections were further evaluated for Illumina MiSeq sequencing, and twelve sequences (2.7–2.8 kb) equivalent to the full-length DNA-A or DNA-B components of begomoviruses were obtained along with eight sequences (~1.3–1.4 kb) equivalent to the begomovirus-associated DNA-satellite components. Four begomovirus sequences obtained from tomato plants were variants of tomato yellow leaf curl virus (TYLCV) with nt sequence identities of 95.3–100%. Additionally, two tomato plants showed a mixed infection of TYLCV and cotton leaf curl Gezira virus (CLCuGeV), okra yellow crinkle Cameroon alphasatellite (OYCrCMA), and okra leaf curl Oman betasatellite (OLCuOMB). Meanwhile, from muskmelon plants, two sequences were closely related (99–99.6%) to the tomato leaf curl Palampur virus (ToLCPalV) DNA-A, whereas two other sequences showed 97.9–100% sequence identities to DNA-B of ToLCPalV, respectively. Complete genome sequences of CLCuGeV and associated DNA-satellites were also obtained from these muskmelon plants. The nt sequence identities of the CLCuGeV, OYCrCMA, and OLCuOMB isolates obtained were 98.3–100%, 99.5–100%, and 95.6–99.7% with their respective available variants. The recombination was only detected in TYLCV and OLCuOMB isolates. To our knowledge, this is the first identification of a mixed infection of bipartite and monopartite begomoviruses associated with DNA-satellites from tomato and muskmelon in Saudi Arabia. The begomovirus variants reported in this study were clustered with Iranian isolates of respective begomovirus components in the phylogenetic dendrogram. Thus, the Iranian agroecological route can be a possible introduction of these begomoviruses and/or their associated DNA-satellites into Saudi Arabia.

Heat is one of the major environmental stressors that negatively affects alfalfa production. Previously, we reported the role of microRNA156 (miR156) in heat tolerance; however, the mechanism and downstream genes involved in this process were not fully studied. To provide further insight, we compared an empty vector control and miR156-overexpressing alfalfa plants (miR156+) after exposing them to heat stress (40 °C) for 24 h. We collected leaf samples for transcriptome analysis to illustrate the miR156-regulated molecular mechanisms underlying the heat stress response. A total of 3579 differentially expressed genes (DEGs) were detected exclusively in miR156+ plants under heat stress using the Medicago sativa genome as a reference. GO and KEGG analysis indicated that these DEGs were mainly involved in “polysaccharide metabolism”, “response to chemical”, “secondary metabolism”, “carbon metabolism”, and “cell cycle”. Transcription factors predicted in miR156+ plants belonged to the TCP family, MYB, ABA response element-binding factor, WRKY, and heat shock transcription factor. We also identified two new SQUAMOSA PROMOTER BINDING PROTEIN-LIKE (SPL) family gene members (SPL8a and SPL12a), putatively regulated by miR156. The present study provided a comprehensive transcriptome profile of alfalfa, identified a number of genes and pathways, and revealed an miR156-regulated network of mechanisms at the gene expression level to modulate heat responses in alfalfa.