ADP-glucose pyrophosphorylase (AGPase) is a heterotetrameric enzyme with two large subunits (LS) and two small subunits (SS). It plays a critical role in starch biosynthesis. We are reporting here detailed structure, function and evolution of the genes encoding the LS and the SS among monocots and dicots. ‘True’ orthologs of maize Sh2 (AGPase LS) and Bt2 (AGPase SS) were identified in seven other monocots and three dicots; structure of the enzyme at protein level was also studied. Novel findings of the current study include the following: (i) at the DNA level, the genes controlling the SS are more conserved than those controlling the LS; the variation in both is mainly due to intron number, intron length and intron phase distribution; (ii) at protein level, the SS genes are more conserved relative to those for LS; (iii) ‘QTCL’ motif present in SS showed evolutionary differences in AGPase belonging to wheat 7BS, T. urartu, rice and sorghum, while ‘LGGG’ motif in LS was present in all species except T. urartu and chickpea; SS provides thermostability to AGPase, while LS is involved in regulation of AGPase activity; (iv) heterotetrameric structure of AGPase was predicted and analysed in real time environment through molecular dynamics simulation for all the species; (v) several cis-acting regulatory elements were identified in the AGPase promoters with their possible role in regulating spatial and temporal expression (endosperm and leaf tissue) and also the expression, in response to abiotic stresses; and (vi) expression analysis revealed downregulation of both subunits under conditions of heat and drought stress. The results of the present study have allowed better understanding of structure and evolution of the genes and the encoded proteins and provided clues for exploitation of variability in these genes for engineering thermostable AGPase.

Leaf rust disease causes severe yield losses in wheat throughout the world. During the present study, high-throughput RNA-Seq analysis was used to gain insights into the role of Lr28 gene in imparting seedling leaf rust resistance in wheat. Differential expression analysis was conducted using a pair of near-isogenic lines (NILs) (HD 2329 and HD 2329 + Lr28) at early (0 h before inoculation (hbi), 24 and 48 h after inoculation (hai)) and late stages (72, 96 and 168 hai) after inoculation with a virulent pathotype of pathogen Puccinia triticina. Expression of a large number of genes was found to be affected due to the presence/absence of Lr28. Gene ontology analysis of the differentially expressed transcripts suggested enrichment of transcripts involved in carbohydrate and amino acid metabolism, oxidative stress and hormone metabolism, in resistant and/or susceptible NILs. Genes encoding receptor like kinases (RLKs) (including ATP binding; serine threonine kinases) and other kinases were the most abundant class of genes, whose expression was affected. Genes involved in reactive oxygen species (ROS) homeostasis and several genes encoding transcription factors (TFs) (most abundant being WRKY TFs) were also identified along with some ncRNAs and histone variants. Quantitative real-time PCR was also used for validation of 39 representative selected genes. In the long term, the present study should prove useful in developing leaf rust resistant wheat cultivars through molecular breeding.