Project description:Background: Maize plants developed typical gray leaf spot disease (GLS) symptoms initiating at the lower leaves and progressing to upper leaves through the season. Leaf material was collected at 77 days after planting, at which stage there were a large number of GLS disease necrotic lesions on lower leaves (8% surface area on average determined by digital image analysis), but very few lesions and only at chlorotic stage on leaves above the ear (average of 0.2% lesion surface area). Method:To collect material that reflected a difference between C.zeina infected B73 leaves and control B73 leaf material, samples were collected from two lower GLS infected leaves (second and third leaf internode below ear) , and two upper leaves with minimal GLS symptoms (second and third internode above ear), respectively. The two lower leaves from each plant were pooled prior to RNA extraction, and the two upper leaves from each plant were pooled prior to RNA extraction. Upper and lower leaf samples from three maize B73 plants were subjected to RNA sequencing individually. The three maize plants were selected randomly as one plant per row from three rows of ten B73 plants each. Result: A systems genetics strategy revealed regions on the maize genome underlying co-expression of genes in susceptible and resistance responses, including a set of 100 genes common to the susceptible response of sub-tropical and temperate maize.
Project description:Apple leaf spot caused by the Alternaria alternata f. sp. mali (ALT1) fungus is one of the most devastating diseases of apple (Malus × domestica). We identified a hairpin RNA (hpRNA)-mediated small RNAs, MdhpRNA277, from apple (cv. ‘Golden Delicious’) that is induced by infection with ALT1. MdhpRNA277 produces mdm-siR277-1 and mdm-siR277-2, which target five R genes, MdRNL1, MdRNL2, MdRNL3, MdRNL4, and MdRNL5, that are expressed at high levels in the resistant apple variety ‘Hanfu’ and at low levels in the susceptible variety ‘Golden Delicious’ following ALT1 infection. MdhpRNA277 is strongly induced in ‘Golden Delicious’ but was not induced in ‘Hanfu’ following ALT1 inoculation. The promoter activity of MdhpRNA277 was much stronger in ‘Golden Delicious’ than in ‘Hanfu’ after ALT1 inoculation. We identified a single nucleotide polymorphism (SNP) in the MdhpRNA277 promoter region between the susceptible variety ‘Golden Delicious’ (pMdhpRNA277-GD) and resistant variety ‘Hanfu’ (pMdhpRNA277-HF). The transcription factor MdWHy binds to pMdhpRNA277-GD, but not to pMdhpRNA277-HF. Transgenic ‘GL-3’ apple lines expressing pMdhpRNA277-GD: MdhpRNA277 were more susceptible to ALT1 infection than were those expressing pMdhpRNA277-HF:MdhpRNA277 due to induced mdm-siR277 accumulation and low levels of expression of the five target R genes. The failure of MdWHy to bind to pMdhpRNA277-HF might contribute to the low levels of MdhpRNA277 and mdm-siR277-1/-2 expression and the high levels of R gene expression and resistance to Alternaria leaf spot in resistant apple varieties. We confirmed that the SNP in pMdhpRNA277 is associated with Alternaria leaf spot resistance by analyzing the progeny of three additional crosses. The SNP identified in this study could be used as a marker to distinguish between apple varieties that are resistant or susceptible to Alternaria leaf spot.
Project description:Three different maize lines were assayed for differential gene expression in mature leaf tissue. Leaves from the Oh43 maize line are more resistant to insect larvae damage than the original parents, lines Oh40B and W8. The goal of the project was to discover genes highly expressed in the Oh43 line that potentially contributes to insect resistance.
Project description:Gray leaf spot (GLS) disease of maize is caused by the fungus Cercospora zeina in African countries, such as South Africa. The plant material was from maize inbred line B73-QTL, which was introgressed with a QTL region for resistance to GLS from the maize inbred line CML444 (Berger et al (2014) BMC Genetics 15 60 www.biomedcentral.com/1471-2156/15/60 ). This QTL was named 10G2_GLS and 10H_GLS from two field trials in KwaZulu-Natal province, South Africa in that study. B73-QTL plants were planted in the field, and subjected to natural infection with C. zeina. This was the same field trial as B73 plants that were sampled for RNAseq and the data reported in Swart et al (2017) Mol Plant Microbe Interact 30 710-724 (2017)(GSE94442). Samples were collected from lower leaves with moderate GLS lesions and younger upper leaves of the same B73-QTL plants with very few immature GLS lesions. The first aim of the experiment was to compare the maize transcriptomes during C.zeina challenge between B73 (from GSE94442 data) and B73-QTL plants (this study). The second aim was to identify novel transcripts expressed from the QTL region, which may underlie the quantitative disease resistance to GLS. The third aim was to identify C. zeina genes expressed in planta during infection.
Project description:Although Cochliobolus miyabeanus is an important fungal leaf pathogen on rice plants worldwide, it is largely neglected by molecular plant phytopathologists. To shed new light on the molecular and genetic basis of the rice – C. miyabeanus interaction, we compared the transcriptome of rice leaves 12h post inoculation to uninfected leaves. Even though usable sources of resistance against brown spot disease caused by C. miyabeanus are scarce, silicon application emerges as a sustainable protection strategy. Many articles report the beneficial effect of silicon on brown spot resistance. however the underlying mechanisms remain largely unclear. The influence of silicon application on the transcriptome of healthy and infected rice leaves 12hpi was compared as well in an attempt to disentangle the modulation of silicon-induced brown spot resistance.
Project description:Mango bacterial leaf spot, which is caused by Xanthomonas critis pv. mangiferaeindicae (Xcm), poses a great threat to the development of mango planting industry.This work is the first to study the changes in gene and protein expressions in mango during Xcm infection. Our findings will provide new ideas for MBLS resistance and valuable genetic resources for the breeding of MBLS-resistant mango.
Project description:Maize husk leaf - the outer leafy layers covering the ear - modulates kernel yield and quality. Despite its importance, however, the genetic controls underlying husk leaf development remain elusive. Our previous genome-wide association study identified a single nucleotide polymorphism located in the gene RHW1 (Regulator of Husk leaf Width) that is significantly associated with husk leaf-width diversity in maize. Here, we further demonstrate that a polymorphic 18-bp InDel (insertion/deletion) variant in the 3' untranslated region of RHW1 alters its protein abundance and accounts for husk leaf width variation. RHW1 encodes a putative MYB-like transcriptional repressor. Disruption of RHW1 altered cell proliferation and resulted in a narrower husk leaf, whereas RHW1 overexpression yielded a wider husk leaf. RHW1 positively regulated the expression of ZCN4, a well-known TFL1-like protein involved in maize ear development. Dysfunction of ZCN4 reduced husk leaf width even in the context of RHW1 overexpression. The InDel variant in RHW1 is subject to selection and is associated with maize husk leaf adaption from tropical to temperate regions. Overall, our results identify that RHW1-ZCN4 regulates a pathway conferring husk leaf width variation at a very early stage of husk leaf development in maize.
Project description:Three different maize lines were assayed for differential gene expression in mature leaf tissue. Leaves from the Oh43 maize line are more resistant to insect larvae damage than the original parents, lines Oh40B and W8. The goal of the project was to discover genes highly expressed in the Oh43 line that potentially contributes to insect resistance. RNA was extracted from a mature leaf (third visible leaf from the top of a 7 leaf plant) of each inbred (Oh43, Oh40B, and W8). cDNA from four biological replicates of each inbred was labeled (indirect method) twice with Cy5 and twice with Cy3. A total of six microarray slides were probed with 12 different labeled cDNAs.
Project description:Gray leaf spot (GLS) disease of maize can be caused by either of two sibling fungal species Cercospora zeina or Cercospora zeae-maydis. These species differ in geographical distribution, for example to date only C. zeina is associated with GLS in Africa. C. zeae-maydis isolates produce the phytotoxin cercosporin in vitro, whereas C. zeina does not. C.zeina was grown in different in vitro conditions to determine if the cercosporin biosynthesis genes were expressed. Furthermore, the choice of a range of different in vitro conditions was aimed at capturing transcript sequences from a broad range of genes to aid in identification of gene models for annotation of the C.zeina genome sequence.