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Lignocellulosic biomass is an abundant byproduct from cereal crops that can potentially be valorized as a feedstock to produce biomaterials. Zea mays CINNAMYL ALCOHOL DEHYDROGENASE 2 (ZmCAD2) is involved in lignification, and is a promising target to improve the cellulose‐to‐glucose conversion of maize stover. Here, we analyzed a field‐grown zmcad2 Mutator transposon insertional mutant. Zmcad2 mutant plants had an 18% lower Klason lignin content, whereas their cellulose content was similar to that of control lines. The lignin in zmcad2 mutants contained increased levels of hydroxycinnamaldehydes, i.e. the substrates of ZmCAD2, ferulic acid and tricin. Ferulates decorating hemicelluloses were not altered. Phenolic profiling further revealed that hydroxycinnamaldehydes are partly converted into (dihydro)ferulic acid and sinapic acid and their derivatives in zmcad2 mutants. Syringyl lactic acid hexoside, a metabolic sink in CAD‐deficient dicot trees, appeared not to be a sink in zmcad2 maize. The enzymatic cellulose‐to‐glucose conversion efficiency was determined after 10 different thermochemical pre‐treatments. Zmcad2 yielded significantly higher conversions compared with controls for almost every pre‐treatment. However, the relative increase in glucose yields after alkaline pre‐treatment was not higher than the relative increase when no pre‐treatment was applied, suggesting that the positive effect of the incorporation of hydroxycinnamaldehydes was leveled off by the negative effect of reduced p‐coumarate levels in the cell wall. Taken together, our results reveal how phenolic metabolism is affected in CAD‐deficient maize, and further support mutating CAD genes in cereal crops as a promising strategy to improve lignocellulosic biomass for sugar‐platform biorefineries.

Although increasing attention has been paid to the relationships between heavy metal and nitrogen (N) availability, the mechanism underlying adaptation to cadmium (Cd) stress in dioecious plants has been largely overlooked. This study examined Cd accumulation, translocation and allocation among tissues and cellular compartments in Populus cathayana Rehder females and males. Both leaf Cd accumulation and root-to-shoot Cd translocation were significantly greater in females than in males under a normal N supply, but they were reduced in females and enhanced in males under N deficiency. The genes related to Cd uptake and translocation, HMA2, YSL2 and ZIP2, were strongly induced by Cd stress in female roots and in males under a normal N supply. Cadmium largely accumulated in the leaf blades of females and in the leaf veins of males under a normal N supply, while the contrary was true under N deficiency. Furthermore, Cd was mainly distributed in the leaf epidermis and spongy tissues of males, and in the leaf palisade tissues of females. Nitrogen deficiency increased Cd allocation to the spongy tissues of female leaves and to the palisade tissues of males. In roots, Cd was preferentially distributed to the epidermis and cortices in both sexes, and also to the vascular tissues of females under a normal N supply but not under N deficiency. These results suggested that males possess better Cd tolerance compared with females, even under N deficiency, which is associated with their reduced root-to-shoot Cd translocation, specific Cd distribution in organic and/or cellular compartments, and enhanced antioxidation and ion homeostasis. Our study also provides new insights into engineering woody plants for phytoremediation.

Seed aging is a process that results in a delayed germination, a decreased germination percentage, and finally a total loss of seed viability. However, the mechanism of seed aging is poorly understood. In the present study, Yliangyou 2 hybrid rice (Oryza sativa L.) seeds were artificially aged at 100% relative humidity and 40 degrees C, and the effect of artificial aging on germination, germination time course and the change in protein profiles of embryo and endosperm was studied to understand the molecular mechanism behind seed aging. With an increasing duration of artificial aging, the germination percentage and germination rate of hybrid rice seeds decreased. By comparing the protein profiles from the seeds aged for 0, 10 and 25 days, a total of 91 and 100 protein spots were found to show a significant change of more than 2-fold (P

To compare the effect of arbuscular mycorrhiza (AM) and P-supplement on N uptake and N assimilation under well-watered or drought-stressed conditions, Glomus intraradices-colonised, P-supplemented non-mycorrhizal (P) and non-mycorrhizal (control) plants of Lolium perenne were exposed to 12 days of water treatment. Leaf water potential (Ψ w), photosynthetic ability, and N and P nutritional status were measured at the beginning (day 0) and end (day 12) of water treatment. N absorption, amino acid and protein synthesis were quantified using the isotopic tracer 15N at day 12. Under well-watered conditions, growth response and physiological parameters were similar in AM and P plants, as compared to controls. Drought (10% water) significantly decreased these parameters in all three treatments. As compared to control plants, the negative impact of water deficit on the Ψ w, photosynthesis, biomass, and N and P content was highly alleviated in AM plants, while only slightly improved or remained the same level in P plants. The effect of AM symbiosis on N absorption and N assimilation was greater than that of the P supplement under well-watered and drought-stressed conditions, and this effect was highly enhanced under drought-stressed conditions. At terminal drought stress on day 12, the effect of AM colonisation on de novo synthesis of amino acids and proteins was 4.4- and 4.8-fold higher than that of the P supplement. These results indicate that the AM symbiosis plays an integrative role in N nutrition by alleviating the negative impacts of drought on N or P uptake and N assimilation, whereas the efficiency of a direct P supplement is very limited under drought-stressed conditions.

In plants, several population types [F2, recombinant inbred lines, backcross inbred lines (BILs), etc.] are used for quantitative trait locus (QTL) analyses. However, dissection of the trait of interest and subsequent confirmation by introgression of QTLs for breeding purposes has not been as successful as that predicted from theoretical calculations. More practical knowledge of different QTL mapping approaches is needed. In this recent study, we describe the detection and mapping of quantitative resistances to downy mildew in a set of 29 BILs of cultivated lettuce (L. sativa) containing genome segments introgressed from wild lettuce (L. saligna). Introgression regions that are associated with quantitative resistance are considered to harbor a QTL. Furthermore, we compare this with results from an already existing F2 population derived from the same parents. We identified six QTLs in our BIL approach compared to only three in the F2 approach, while there were two QTLs in common. We performed a simulation study based on our actual data to help us interpret them. This revealed that two newly detected QTLs in the BILs had gone unnoticed in the F2, due to a combination of recessiveness of the trait and skewed segregation, causing a deficit of the wild species alleles. This study clearly illustrates the added value of extended genetic studies on two different population types (BILs and F2) to dissect complex genetic traits

The genetic architecture of crop domestication is generally characterized by three trends: relatively few genomic regions with major QTL effects are involved, QTL are often clustered, and alleles derived from the crop do not always contribute to the crop phenotype. We have investigated the genetic architecture of lettuce using a recombinant inbred line population from a cross between a crop Lactuca sativa (‘Salinas’) and its wild relative L. serriola. Few genomic regions with major QTL, plus various intermediate QTL, largely control the transition from wild to cultivated Crisphead lettuce. Allelic effects of all major QTL were in the expected direction, but there were intermediate QTL where the crop contributed to the wild phenotype and vice versa. We found two main regions with clusters of QTL, one on linkage group 3, where the crop allele induced lower seed output, another on linkage group 7, where the crop allele caused a delay in flowering time. Potentially, knowledge of genetic changes due to the domestication could be relevant for the chance that a transgene inserted in a crop genome will spread to wild relatives due to hitchhiking effects. If a transgene would be inserted in one of these regions, background selection on the crop alleles may lead to a reduced fitness of hybrids with the transgene. QTL research on the effects of domestication genes can thus indicate regions in the crop genome that are less likely to introgress, although these still need to be verified under field conditions.

In plants, several population types [F2, recombinant inbred lines, backcross inbred lines (BILs), etc.] are used for quantitative trait locus (QTL) analyses. However, dissection of the trait of interest and subsequent confirmation by introgression of QTLs for breeding purposes has not been as successful as that predicted from theoretical calculations. More practical knowledge of different QTL mapping approaches is needed. In this recent study, we describe the detection and mapping of quantitative resistances to downy mildew in a set of 29 BILs of cultivated lettuce (L. sativa) containing genome segments introgressed from wild lettuce (L. saligna). Introgression regions that are associated with quantitative resistance are considered to harbor a QTL. Furthermore, we compare this with results from an already existing F2 population derived from the same parents. We identified six QTLs in our BIL approach compared to only three in the F2 approach, while there were two QTLs in common. We performed a simulation study based on our actual data to help us interpret them. This revealed that two newly detected QTLs in the BILs had gone unnoticed in the F2, due to a combination of recessiveness of the trait and skewed segregation, causing a deficit of the wild species alleles. This study clearly illustrates the added value of extended genetic studies on two different population types (BILs and F2) to dissect complex genetic traits