Mutants defective in chloroplast development or photosynthesis are liable to accumulate higher levels of anthocyanin in photo-oxidative stress.However,regulatory mechanisms of anthocyanin biosynthesis in the mutants remain unclear.Here,we investigated the mechanism by which the deletion of thylakoid formation1（THF1） leads to an increased level of anthocyanin in Arabidopsis thaliana L.Physiological and genetic evidence showed that the increased level of anthocyanin in thf1 is dependent on coronatine-insensitive1（COM）signaling.Our data showed that thf1 had higher levels of basalα-linolenic acid（α-LeA）,and methyl jasmonate（JA）-induced α-LeA and 12-oxophytodienoic acid（OPDA） than the wild type（WT）.Consistently,expression levels of phospholipase genes including pPLAIIα and PLA-Iγ1 were elevated in thf1.Furthermore,inhibition of lipase activity by bromoenol lactone,a specific inhibitor of plant pPLA,led to producing identical levels of anthocyanins in WT and thf1 plants.Interestingly,OPDA biosynthesis was triggered by light illumination in isolated chloroplasts,indicating that new protein import into chloroplasts is not required for OPDA biosynthesis.Thus,we conclude that the elevated anthocyanin accumulation in thf1 is attributed to an increase in JA levels.This JA-mediated signaling to coordinate plant metabolism and growth in stress may be conserved in other photosensitive mutants.
Yi GanHong LiYe XieWenjuan WuMaoyin LiXuemin WangJirong Huang
Anthocyanin biosynthesis is regulated by a conserved transcriptional MBW complex composed of MYB,b HLH and WD40 subunits. However, molecular mechanisms underlying transcriptional regulation of these MBW subunits remain largely elusive. In this study, we isolated an Arabidopsis mutant that displays a constitutive red color in aboveground tissues with retarded growth phenotypes. In the presence of sucrose, the mutant accumulates more than 3-fold anthocyanins of the wild type(WT), but cannot produce anthocyanins as WT in the absence of sucrose. Map-based cloning results demonstrated that the mutation occurs in the locus At4 G01000, which encodes a conserved nuclear-localized ubiquitin-like(UBL) superfamily protein, silencing defective 2(SDE2), in eukaryotes. SDE2 is ubiquitously expressed in various tissues. In the sucrose-induced anthocyanin biosynthesis, SDE2 expression was not responded to sucrose treatment at the early stage but was enhanced at the late stage. SDE2 mutations result in upregulation of anthocyanin biosynthetic and regulatory genes. Yeast-two hybrid analysis indicated that SDE2 has no direct interaction with the MYB transcription factor PAP1 and b HLH factor TT8, indicating that SDE2 is a indirect factor to affect anthocyanin accumulation. Taking together, our data suggest that SDE2 may play a role in finely coordinating anthocyanin biosynthesis with other biological processes.
Understanding the genetic mechanism underlying folate biosynthesis and accumulation in rice would be beneficial for breeding high folate content varieties as a cost-effective approach to addressing widespread folate deficiency in developing countries. In this study, the inheritance of rice grain folate content was investigated in the Lemont/Teqing recombinant inbred lines and the Koshihikari/Kasalath//Koshihikari backcross inbred lines. 264 F12 recombinant inbred lines（RILs） and 182 BC1F10 backcross inbred lines（BILs） with their parents planted in randomized complete blocks with two replicates in 2010, and RILs harvested in 2008 were used for QTL detection using inclusive composite interval mapping（ICIM） method. In the RIL population, two QTLs, denoted by qQTF-3-1 and qQTF-3-2（QTF, quantitative total folate）, explaining 7.8% and 11.1-15.8% of the folate content variation were detected in one or two years, respectively. In the BIL population, a QTL, denoted by qQTF-3-3, was detected, explaining 25.3% of the variation in folate content. All the positive alleles for higher folate content were from the high-folate parents, i.e., Teqing and Kasalath. The known putative folate biosynthesis genes do not underlie the QTLs detected in this study and therefore may be novel loci affecting folate content in milled rice. QTLs identified in this study have potential value for marker assisted breeding for high-folate rice variety.
Plants undergo a series of developmental transitions during their life cycle. After seed germination, plants pass through two distinct phases: the vegetative phase in which leaves are produced and the reproductive phase in which flowering occurs. Based on the reproductive competence and morphological changes, the vegetative phase can be further divided into juvenile and adult phases. Here, we demonstrate that the difference between juvenile and adult phase of Nicotiana tabacum is characterized by the changes in leaf size, leaf shape as well as the number of leaf epidermal hairs(trichomes). We further show that miR156, an age-regulated microR NA, regulates juvenile-to-adult phase transition in N. tabacum. Overexpression of miR156 results in delayed juvenile-to-adult transition and flowering. Together, our results support an evolutionarily conserved role of miR156 in plant developmental transitions.
Sesquiterpenoids are a class of 15-carbon secondary metabolites that play diverse roles in plant adaptation to environment. Cotton plants accumulate a large amount of sesquiterpene aldehydes （including gossypol） as phytoalexins against pathogens and herbivores. They are stored in pigment glands of aerial organs and in epidermal layers of roots. Several enzymes of goss- ypol biosynthesis pathway have been characterized, including 3-hydroxy-3-methylglutaryl coenzyme A reductase （HMGR） and farnesyl diphosphate synthase （FPS） that catalyze the formation of the precursor farnesyl diphosphate （FPP）, （＋）-6-cadinene synthase （CDN） which is the first enzyme committed to gossypol biosynthesis, and the downstream enzymes of CYP706B 1 and methyltransferase. Expressions of these genes are tightly regulated during cotton plants development and in- duced by jasmonate and fungi elicitors. The transcription factor GaWRKY1 has been shown to be involved in gossypol path- way regulation. Recent development of new genomic platforms and methods and releases of diploid and tetraploid cotton ge- nome sequences will greatly facilitate the elucidation of gossypol biosynthetic pathway and its regulation.
Xiu TianJuxin RuanJinquan HuangXin FangYingbo MaoLingjian WangXiaoya ChenChangqing Yang
