DNA Methylation Mediated by a MicroRNA Pathway [鍏ㄦ枃] [鎰熻阿绾㈠啗闀垮緛璁哄潧鐨刴hl]

In plants, the known microRNAs (miRNAs) are produced as 锝�21 nucleotide (nt) duplexes from their precursors by Dicer-like 1 (DCL1). They are incorporated into Argonaute 1 (AGO1) protein to regulate target gene expression primarily through mRNA cleavage. We report here the discovery of a class of miRNAs in the model monocot rice (Oryza sativa). These are 24 nt in length and require another member of the Dicer family, DCL3, for their biogenesis. The 24 nt long miRNAs (lmiRNAs) are loaded into AGO4 clade proteins according to hierarchical rules, depending on the upstream biogenesis machinery and the 5鈥�-terminal nucleotide. We demonstrated that lmiRNAs direct DNA methylation at loci from which they are produced as well as in trans at their target genes and play roles in gene regulation. Considered together, our findings define a miRNA pathway that mediates DNA methylation.

Small RNAs serve as a genetic buffer against genomic shock in Arabidopsis interspecific hybrids and allopolyploids.

缇庡浗澶氫釜澶у鍒嗗瓙鐢熺墿鐮旂┒涓績鍜屼腑绉戦櫌閬椾紶鎵�鑱斿悎 鍙戝湪PNAS涓� 锛屾枃涓彁鍒颁簡涓�涓湁瓒ｇ殑鍚嶅瓧鈥済enetic buffer鈥濓紝鏆備笖缈昏瘧鎴愨�滈仐浼犵紦鍐插墏鈥濆惂銆�

鍦ㄧ浉杩戠殑鐗╃鍜屼腑闂存潅浜ょ涓爺绌秙mall RNA 琛ㄨ揪澶氭牱鎬э紝鐮旂┒瀵硅薄涓轰袱绉嶆嫙鍏拌姤妞嶇墿Arabidopsis thaliana 鍜� A. arenosa.锛屽畠浠殑寮傛簮鍥涘�嶄綋Arabidopsis suecica,缁煎悎璇ュ洓鍊嶄綋鐨勬潅浜ゆ牚绯诲悗浠�(F(1) and F(7))涓婏紝缁撴灉鍙戠幇閲嶅鍜岃浆搴у瓙鐩稿叧鐨剆iRNA鍦ˋrabidopsis thaliana 鍜� A. arenosa涓〃杈惧樊寮傚緢澶э紝杩欑宸窛鍙樺寲鐨剆iRNA缇ゅ湪F1涓篃寰堟槑鏄炬�ュ墽鍙樺寲锛屼絾鍦ˋrabidopsis suecica鍜孎7涓繚鎸佺ǔ瀹氾紝miRNA 鍜� tasiRNA鐨勫簭鍒楀湪绉嶉棿淇濆畧浣嗘槸琛ㄨ揪妯″紡鍦ㄥ紓婧愬洓鍊嶄綋鍙婂叾浜叉湰涓彉鍖栧緢澶с�傘�傘�傛�讳箣锛岀粨璁篻enetic buffer 灏辨槸褰撴潅浜ょ鍐呭彂鐢焔enomic shock鏃讹紝涓轰簡鏌撹壊璐ㄥ拰鍩哄洜缁勭殑鍜岃皭绋冲畾锛岀浉鍏崇殑siRNA缇ゅ彂鎸ヤ簡浣滅敤锛岃�岃〃杈惧樊寮傜殑miRNA鍒欏紩瀵肩潃gene鍦ㄨ〃杈句笂鐨勫彉鍖栧拰鐢熸椿鍔涚殑閫傚簲鎬с��

PS:鎯冲埌浠婂勾浣滅墿鎵�閲屼篃鍙戜簡绡囧叧浜庡皬楹﹀拰鏌愪竴杩戞簮鐗╃small RNA鍒嗗竷姣旇緝鐨勬枃绔犲彂鍦‵unct Integr Genomics IF 3.8锛岀湅鏍峰瓙鏂囩珷涓嶅厜IDEA鍑哄僵锛屾悶澶栦氦鍜屽鍚堜綔涔熸槸鐜嬮亾銆�

Small RNAs, including microRNAs (miRNAs), small interfering RNAs (siRNAs), and trans-acting siRNAs (tasiRNAs), control gene expression and epigenetic regulation. Although the roles of miRNAs and siRNAs have been extensively studied, their expression diversity and evolution in closely related species and interspecific hybrids are poorly understood. Here, we show comprehensive analyses of miRNA expression and siRNA distributions in two closely related species Arabidopsis thaliana and Arabidopsis arenosa, a natural allotetraploid Arabidopsis suecica, and two resynthesized allotetraploid lines (F(1) and F(7)) derived from A. thaliana and A. arenosa. We found that repeat- and transposon-associated siRNAs were highly divergent between A. thaliana and A. arenosa. A. thaliana siRNA populations underwent rapid changes in F(1) but were stably maintained in F(7) and A. suecica. The correlation between siRNAs and nonadditive gene expression in allopolyploids is insignificant. In contrast, miRNA and tasiRNA sequences were conserved between species, but their expression patterns were highly variable between the allotetraploids and their progenitors. Many miRNAs tested were nonadditively expressed (deviating from the mid-parent value, MPV) in the allotetraploids and triggered unequal degradation of A. thaliana or A. arenosa targets. The data suggest that small RNAs produced during interspecific hybridization or polyploidization serve as a buffer against the genomic shock in interspecific hybrids and allopolyploids: Stable inheritance of repeat-associated siRNAs maintains chromatin and genome stability, whereas expression variation of miRNAs leads to changes in gene expression, growth vigor, and adaptation.

Clusters and superclusters of phased small RNAs in the developing inflorescence of rice 锛圥DF)

genome research 杩戝嚑骞村彂浜嗕笉灏戠瘒鍏充簬small RNA锛圡iRNA锛夌殑鏂囩珷锛屾柊鐨勫皬RNA锛屼互鍙婂湪鍩哄洜缁勫唴鐨勫垎甯� 瑙勫緥鎴栬�呭仛绉嶉棿绉嶅唴姣旇緝鐮旂┒锛岄兘鑴变笉寮�涓板瘜鐨勫熀鍥犵粍瀛︾煡璇嗭紝瀵规按绋诲皬RNA浠庡垵鏈熷埌瀵瑰悇涓粍缁囧悇涓椂鏈熷缓搴撳垎鏋愶紝杩欏凡缁忔槸绗琋绡囦簡锛岄鐩鐨勬槸鑺辨湡鐨勫皬RNA锛岋紙鍏跺疄鍟ラ兘鍋氫簡锛夛紝siRNA鏃╂湡涔熸湁浜哄仛杩囩皣鐘跺垎甯冪殑鐮旂┒锛屼絾鏄偅鏃跺�欏鏁翠釜small RNA鐨勪簡瑙ｈ繕娌￠偅涔堜赴瀵屽锛岀幇鍦ㄥ洖杩囧ご鏉ュ啀鍒嗘瀽涓�鐣紝閰嶄笂婕備寒鐨勫浘鐗囷紝鍙堟槸涓�绡囧ソ鏂囥��

涓轰簡鐮旂┒姘寸ɑ鍙戣偛杩囩▼涓璼mall RNA鐨勮皟鑺備綔鐢紝瀵规垚鐔熷彾鐗囷紝鏍癸紝鑼庡拰鑺眘mall RNA鍋�454娴嬪簭鍒嗘瀽锛堟湁閽辨湁鎶�鏈晩锛侊級锛宑luster澶氱敱涓ょsmall RNA缁勬垚24-nt RNA鍜�21锛峮tRNA锛屽畠浠殑鍒嗗竷鍜岃〃杈炬ā寮忛兘涓嶄竴鏍枫��24锛峮tRNA瀵岄泦鍦ㄥ熀鍥犵粍鐨勯噸澶嶅尯鍩熷苟涓斿湪鍥涚缁勭粐閮借〃杈句絾鏄尯鍒笉澶э紝鏂囩珷缁欑殑缁撹鏄�24锛峮t RNA瀵归噸澶嶅尯鍏冧欢鐨勬矇榛樿捣鐫�housekeeping 聽鐪嬪鍔熻兘锛岃��21nt RNA缁勬垚铏藉皯锛屼笖鍦ㄥ熀鍥犵粍鍒嗗竷涓婇潪闅忔満锛� 鍗磋兘琚垎鎴�31 superclusters,锛坢iRNA鏋滅劧灏忛褰撳锛夛紝杩欑被閲嶅鍜宻mall RNA鐨勫舰鎴愮浉鍏筹紝骞朵笖浼樺厛鍦ㄨ姳鏈熻〃杈撅紝鍏朵腑杩樺寘鎷竴閮ㄥ垎閫�鍖栫殑22nt RNA锛岀爺绌惰繕鍙戠幇涓�绫绘柊鍨媘iRNA鍙兘浠嬪cleavage of the cluster motif銆傘�傘��

To address the role of small regulatory RNAs in rice development, we generated a large data set of small RNAs from mature leaves and developing roots, shoots, and inflorescences. Using a spatial clustering algorithm, we identified 36,780 genomic groups of small RNAs. Most consisted of 24-nt RNAs that are expressed in all four tissues and enriched in repeat regions of the genome; 1029 clusters were composed primarily of 21-nt small RNAs and, strikingly, 831 of these contained phased RNAs and were preferentially expressed in developing inflorescences. Thirty-eight of the 24-mer clusters were also phased and preferentially expressed in inflorescences. The phased 21-mer clusters derive from nonprotein coding, nonrepeat regions of the genome and are grouped together into superclusters containing 10鈥�46 clusters. The majority of these 21-mer clusters (705/831) are flanked by a degenerate 22-nt motif that is offset by 12 nt from the main phase of the cluster. Small RNAs complementary to these flanking 22-nt motifs define a new miRNA family, which is conserved in maize and expressed in developing reproductive tissues in both plants. These results suggest that the biogenesis of phased inflorescence RNAs resembles that of tasiRNAs and raise the possibility that these novel small RNAs function in early reproductive development in rice and other monocots.

MicroRNAs and Their Regulatory Roles in Plants

05骞寸殑缁艰堪锛岃櫧鐒跺湪small RNA浜х敓鍜岃皟鎺ф満鐞嗕笂寰堝 鍐呭宸叉洿鏂帮紝浣嗕綔涓轰竴绡囩爺绌舵鐗﹕mall RNA鐨勫叆闂ㄦ枃绔犺繕鏄緢濂界殑銆�

MicroRNAs (miRNAs) 鏄皬鍐呮簮鎬NA鍦ㄦ鐗╁拰鍔ㄧ墿涓皟鑺傚熀鍥犺〃杈撅紝杩欎簺21nt鐨凴NA鐢辩被DICER閰朵粠闀跨殑鍒濆杞綍鏈笂鐨勮寧鐜粨鏋勪笂鍔犲伐鑰屾潵锛屽啀瀵煎叆娌夐粯澶嶅悎浣擄紝鍦ㄥ鍚堜綋涓垎瑁備簰琛ョ殑mRNA銆俶iRNA浠嬪鐨勫熀鍥犺皟鎺у妞嶇墿鍙戣偛杩涚▼鏈夐噸瑕佸奖鍝嶏紝澶氫互涓�浜涚紪鐮佽浆褰曞洜瀛愬拰F锛峛ox铔嬬櫧浣滀负闈跺熀鍥犳潵锛岃�岃繖浜涢澏鍩哄洜鎭版槸璋冩帶缃戠粶鐨勪腑蹇冪幆鑺傘��

MicroRNAs (miRNAs) are small, endogenous RNAs that regulate
gene expression in plants and animals. In plants, these 鈭�21- nucleotide RNAs are processed from stem-loop regions of long primary transcripts by a Dicer-like enzyme and are loaded into silencing complexes, where they generally direct cleavage of complementary mRNAs. Although plant miRNAs have some conserved functions extending beyond development, the importance of miRNA-directed gene regulation during plant development is now particularly clear. Identified in plants less than four years ago, miRNAs are already known to play numerous crucial roles at each major stage of development鈥攖ypically at the cores of gene regulatory networks, targeting genes that are themselves regulators, such as those encoding transcription factors and F-box proteins.

Starch Degradation

鍓嶅嚑骞寸殑缁艰堪浜� 鐮旂┒瀵硅薄涓昏鏄嫙鍏拌姤锛屽彾鐗囦腑鐨勬穩绮夐檷瑙AHWAY锛屼篃鍒嗘瀽浜嗗拰浼犵粺鐨勬穩绮夊偍钘忓櫒瀹樿儦涔充腑PATHWAY鐨勫紓鍚�

杩戞湡瀵规嫙鍏拌姤鍙剁墖澶滈棿娣�绮夐檷瑙ｇ爺绌惰〃鏄庤繖绫婚�斿緞鍜屾暀绉戜功涓婄殑妯″紡宸埆杩樻槸姣旇緝澶х殑锛岃櫧鐒舵湁浜涢�斿緞宸茬粡鐭ラ亾锛屼絾浠嶆湁璁稿鏈夊緟鐮旂┒銆傛潵鑷穩绮夐绮掔殑钁¤仛绯栫敱尾锛嶆穩绮夐叾姘磋В鎴愰害鑺界硸骞惰緭鍑哄彾缁夸綋銆傚湪缁嗚優璐ㄤ腑锛岄害鑺界硸鏄痶ransglucosylation鍙嶅簲鐨勫熀璐紝鐢熸垚钁¤悇绯杇lucose 鍜� glucosylated 鍙椾綋鍒嗗瓙銆傛槸浣曠閰舵敾鍑绘穩绮変綋鐢熸垚钁¤仛绯栵紝鐢熸垚浣曠鍙椾綋鍒嗗瓙杩樹笉鐭ラ亾銆傛嫙鍏拌姤鍙剁墖鐨勫厜鍚堝櫒瀹樹腑娣�绮夌殑鐬椂绉疮鍙婂叾閫斿緞鍦ㄥ叾浠栫墿绉嶄腑涔熼�傜敤锛屼絾瀵逛簬璋风被鐨勮儦涔冲拰璞嗙被鐨勬灉瀹炴潵璇存穩绮夌Н绱ā寮忚繕鏄紶缁熼�斿緞锛岃繖绡囨枃绔犱篃闃愯堪浜嗕笉鍚屼綋绯讳箣闂寸殑鍏宠仈鍜屽尯鍒��

Recent research reveals that starch degradation in Arabidopsis leaves at night is significantly different from the 鈥渢extbook鈥� version of this process.Although parts of the pathway are now understood, other parts remain to be discovered. Glucans derived from starch granules are hydrolyzed via 尾-amylase to maltose, which is exported from the chloroplast. In the cytosol maltose is the substrate for a transglucosylation reaction, producing glucose and a glucosylated acceptor molecule. The enzyme that attacks the starch granule to release glucans is not known, nor is the nature of the cytosolic acceptor molecule. An Arabidopsis-type pathway may operate in leaves of other species, and in nonphotosynthetic organs that accumulate starch transiently. However, in starchstoring organs such as cereal endosperms and legume seeds, the process differs from that in Arabidopsis and may more closely resemble the textbook pathway. We discuss the differences in relation to the biology of each system.

A novel superior factor widely controlling the rice grain quality

from Tokyo University of Science etc.

鑳氫钩鐨勭敓鎴愯繃绋嬩富瑕佸寘鎷偍钘忔穩绮夌殑鍚堟垚鍜岃泲鐧界殑绉疮銆� 杩欎竴杩囩▼褰撳彈鍒伴伃閬囬�嗗鑳佽揩鏃朵緥濡傞珮娓╀細鏀跺埌寮虹儓褰卞搷锛屽洜姝わ紝鍏ㄧ悆姘斿�欏彉鏆栫殑瓒嬪娍浼氬椋熺墿鐨勪骇閲忎骇鐢熸瀬澶у▉鑳� 銆傛穩绮夊悎鎴愬拰铔嬬櫧璐棌閫斿緞涓殑閰剁被鐩镐簰浣滅敤锛岀敓鎴愭按绋昏儦涔筹紝浣嗗叾璋冩帶鏈虹悊杩樹笉鏄庝簡銆傛湰鐮旂┒鍙戠幇浜嗕竴涓柊鐨勮皟鎺у瓙OsCEO1,浣滅敤鏄儦涔冲湪鐏屾祮鏃舵湡鐨勫紩瀵间綋銆俧lo锛�2鐨勮〃鍨嬬被浼间簬鍙楀埌楂樻俯褰卞搷鐨勪骇鐢熺殑绮夎川鎬х姸锛岃鏄庤繖涓�鍩哄洜瀵归珮娓╄儊杩晱鎰� 銆傚flo2鍥句綅鍏嬮殕鍒扮殑OsCEO1涓庡凡鐭ョ殑鍔熻兘鍩哄洜閮戒笉瀛樺湪鍚屾簮鎬э紝瀹冨睘浜庝竴涓潪淇濆畧鐨勫熀鍥犲鏃忥紝缂栫爜1720涓皑鍩洪吀锛屽寘鍚竴涓笁瑙掑洓鑲介噸澶嶅尯锛圱PR锛夛紝鍙兘鍙備笌铔嬬櫧浜掍綔銆傞叺姣嶅弻鏉傛壘鍑�1涓湭鐭ョ殑鏅氭湡鑳氳儙鍙戣偛鍚屾簮铔嬬櫧鍙�1涓亣瀹歨elix-loop-helix铔嬬櫧浣滅敤OsCEO1鐨勭洿鎺ヤ簰浣滃璞★紝缁撴灉涓苟娌℃湁涓庢穩绮夎泲鐧借串钘忓悎鎴愮浉鍏崇殑閰剁被锛岃�屽湪flo2绐佸彉浣撲腑锛屽緢澶氳繖绫荤殑閰讹紝涓昏鏄亣瀹氱殑璋冩帶铔嬬櫧锛岃〃杈句笂閮戒笅璋冦�傛�讳箣锛岀爺绌惰〃鏄庯紝OsCEO1鍙兘鍦ㄦ暣涓儦涔崇敓鎴愰�斿緞鐨勪笂娓歌皟鎺э紝骞跺楂樻俯鑳佽揩鐨勫搷搴旇捣鐫�閲嶈浣滅敤銆�

Synthesis of storage starch and protein accumulation is the main action of endosperm organogenesis in term of the economic importance of rice. This event is strongly disturbed by abiotic stresses such as high temperature; thus, the upcoming global warming will cause a crisis with a great impact on food production1,2. The enzymes for the protein storage and starch synthesis pathway should work in concert to carry out the organogenesis of rice endosperm3鈥�5, but the regulatory mechanism is largely unknown. Here we show that a novel regulatory factor, named OsCEO1, acts as the conductor of endosperm organogenesis during the rice grain filling stage. The physiological properties of floury-endosperm-2 (flo2) mutants showed many similarities to symptoms of grains developed under high-temperature conditions, suggesting important roles of the responsible gene in sensitivity to high-temperature stress. Our map-based cloning identified the responsible gene for the flo2 mutant, OsCEO1, which has no homology to any genes of known function. The OsCEO1 belongs to a novel conserved gene family and encodes a protein composed of 1,720 amino acid residues containing a TPR(tetratricopeptide repeat) motif, which is considered to mediate a protein-protein interaction. The yeast two-hybrid analysis raised an unknown protein showing homology to a late embryogenesis abundant protein and a putative basic helix-loop-helix protein as candidates for the direct interactor for OsCEO1, whereas no enzyme genes for the synthesis of storage substances were detected. The flo2 mutant exhibited reduced expression of several genes for putative regulatory proteins as well as many enzymes involved in storage starch and proteins. These results suggest that OsCEO1 is a superior conductor of the novel regulatory cascade of endosperm organogenesis and may have important roles in the response to high-temperature stress.

Overexpression of BiP has inhibitory effects on the accumulation of seed storage proteins in endosperm cells of rice聽 [涓嬭浇]

璐棌铔嬬櫧鍦ㄧ瀛愭垚鐔熻繃绋嬩腑鐗瑰紓澶ч噺鍚堟垚骞剁粡鐢卞唴璐ㄧ綉娌夌Н鍦ㄨ泲鐧戒綋锛圥B锛夊唴锛岃繖涓�绉嶇Н绱繃绋嬬敱ER浼翠荆濡侭iP锛孭DI绛変粙瀵笺�備负浜嗙爺绌惰繖浜涗即渚ｈ泲鐧界殑浣滅敤鍜屽畠浠笌绉嶅瓙璐棌铔嬬櫧绉疮姘村钩鍙樺寲涔嬮棿鐨勮仈绯伙紝浠ヨ儦涔崇壒寮傚惎鍔ㄥ瓙glutelin promoter鍦ㄦ鏍儦涔充腑杩囪〃杈綛ip鍜孭DI銆侾DI杩囪〃杈炬鏍殑琛ㄥ瀷鍜學T宸笉澶氾紝浣咮ip杩囪〃杈炬鏍憟鐜颁笉閫忔槑锛屽叿浣撹〃鍨嬩负绮夎川floury鍜岀毐缂﹕hrink锛岃串钘忚泲鐧藉拰娣�绮夊惈閲忕殑姘村钩閮戒綆浜嶹T銆傛湁瓒ｇ殑鏄紝鍦ㄨ浆鍖栨牚涓紝涓嶅厜鏉ヨ嚜ER鐨凱B-I鏋勫瀷鏀瑰彉锛岃�屼笖杩樹骇鐢熶簡鏂扮殑绫籔B缁撴瀯锛岃缁撴瀯鍖呮嫭BiP锛屽惈璋疯泲鐧界殑楂樼數瀛愬瘑搴﹀熀璐ㄥ拰鍚胺閱囨憾铔嬬櫧鐨勪綆鐢靛瓙瀵嗗害鍩鸿川锛屽苟涓旇繕闄勭潃澶氭牳绯栦綋锛岀爺绌舵帹娴嬭繖绫绘瀯鍨嬪彲鑳藉睘浜嶦R浜х敓鐨凱B-I鐨勮鐢熺墿锛屽畠浜х敓浜庡唴璐ㄧ綉锛屽苟瀵圭瀛愯泲鐧界殑缈昏瘧锛屾姌鍙犲拰浼犻�佹湁鎶戝埗浣滅敤銆�

Seed storage proteins are specifically and highly synthesized during seed maturation and are deposited into protein bodies (PBs) via the endoplasmic reticulum (ER) lumen. The accumulation process is mediated by ER chaperones such as luminal binding protein (BiP) and protein disulfi de isomerase (PDI). To examine the role of ER chaperones and the relationship between ER chaperones and levels of
accumulation of seed storage proteins, we generated transgenic rice plants in which the rice BiP and PDI genes were overexpressed in an endosperm-specifi c manner under the control of the rice seed storage protein glutelin promoter. The seed phenotype of the PDI overexpressing transformant was almost identical to that of the wild type, whereas overexpression of BiP resulted in transgenic rice seed that displayed an opaque phenotype with floury and shrunken features. In the BiP-overexpressing line, the levels of accumulation of seed storage proteins and starch contents were signifi cantly lower compared with the wild type. Interestingly, overproduction of BiP in the endosperm of the transformant not only altered the morphological
structure of ER-derived PB-I, but also generated unusual new PB-like structures composed of a high electron density matrix containing glutelin and BiP and a low electron density matrix containing prolamins. Notably, polysomes were attached around the aberrant PB-like structures, indicating that this aberrant structure is an ER-derived
PB-I derivative. These results suggested that the PB-like structure may be formed in the ER lumen, resulting in inhibition of translation, folding and transport of seed proteins.

Knockout of a starch synthase gene OsSSIIIa/Flo5causes white-core floury endosperm in rice (Oryza sativa L.)
鐮旂┒SSIIIa 鍦ㄩ鏋滄穩绮夊悎鎴愪腑鐨勪綔鐢紝T锛岲NA鎻掑叆绐佸彉浣揻lo5锛�1鍜宖lo5锛�2鐨勮〃鍨嬫槸绮夎川蹇冪櫧锛屼负涓棿閮ㄥ垎鐨勬穩绮変綋鏉炬暎.鍒╃敤X-ray琛嶅皠鍒嗘瀽鍙戠幇flo5娣�绮夌粨鏅跺害鐩稿閲庣敓鍨嬭“閫�锛孌P 30鐨勯暱閾炬垚鍒嗗噺灏戯紝鍚屾椂DP 6 鍒� 8 and涓嶥P 16 鍒� 20鐨勯摼鍨嬩篃鍑忓皯锛屽彧鏈塂P 9 鍒� 15 鍜� DP22 鍒� 29澧炲锛屽埄鐢ㄥ樊閲忔壂鎻忛噺鐑硶DSC锛岀硦鍖栨俯搴﹂檷浣�1锛�5搴︺�傝繘涓�姝ラ槓鏄嶰sSSIIIa/Flo5鍜屽叾浠栧悓绫籗S寮傛瀯浣撳湪娣�绮夊悎鎴愪腑鐨勪綔鐢ㄣ��

To elucidate the role of SSIIIa during starch synthesis in rice (Oryza sativa L.) endosperm, we characterized null mutants of this gene, generated by T-DNA insertions. Scanning electron microscope (SEM) analysis revealed that the starch granules in these mutants are smaller and rounder compared with the wild type controls, and that the mutant
endosperm is characterized by a loosely packed central portion exhibiting a floury-like phenotype. Hence, the OsSSIIIa (Oryza sativa SSIIIa) mutations are referred to as white-core floury endosperm 5-1 (flo5-1) and flo5-2. Based upon their X-ray diffraction patterns, the crystallinity聽endosperm starch, we found that flo5-1 and flo5-2 mutants have reduced the content of long chains with degree of polymerization (DP) 30 or greater compared with the controls. This suggests that OsSSIIIa/Flo5 plays an important role in generating relatively long
chains in rice endosperm. In addition, DP 6 to 8 and DP 16 to 20 appeared to be reduced in endosperm starch of flo5-1 and flo5-2, whereas DP 9 to 15 and DP 22 to 29 were increased in these mutants. By the use of differential scanning calorimetry (DSC), the gelatinization
temperatures of endosperm starch were found to be 1鈥�5 C lower than those of the control. We propose a distinct role for OsSSIIIa/Flo5 and the coordinated action of other SS isoforms during starch synthesis in the seed endosperm of rice.

White-core endosperm floury endosperm-4 in rice is generated by knockout mutations in the C4-type pyruvate orthophosphate dikinase gene (OsPPDKB)

蹇冪櫧琛ㄥ瀷鐨刦lo4姘寸ɑ绐佸彉浣撻�氳繃SEM鍙互鎵弿鍒颁腑蹇冮儴浣嶆澗鏁ｇ殑娣�绮夊紓甯歌В鏋勶紝绐佸彉浣嶇偣鏄疶锛岲NA鎻掑叆缂栫爜涓欓叜閰哥７閰哥洂婵�閰剁殑OsPPDKB鍩哄洜绗簲澶栨樉瀛愪腑锛屾灉瀹炵殑閲嶉噺姣旈噹鐢熷瀷瑕佽交涓�6锛咃紝娣�绮夊惈閲忕浉浼间絾鎬昏泲鐧藉惈閲忓澶氥�傝嚜鑺卞彈绮惧悗10澶㎡sPPDKB鐨勮〃杈鹃兘鏄庢樉澧炲锛屼富瑕佸湪鑳氫钩锛岀硦绮夊眰锛岃儦涓〃杈俱�傜爺绌剁粨鏋滆〃鏄嶱PDKB璋冭妭浜嗛鏋滃彂鑲茶繃绋嬩腑鐨勭⒊浠ｈ阿閫斿緞

We have isolated a floury endosperm-4 (flo4) rice mutant with a floury-white endosperm but a normal outer portion. Scanning electron microscopic analysis revealed that this abnormal endosperm consisted of loosely packed starch granules. The mutant phenotype was generated by T-DNA insertion into the fifth intron of the OsPPDKB gene encoding pyruvate orthophosphate dikinase (PPDK). Plants containing flo4-1 produced no OsPPDKB transcript or the OsPPDKB protein in their developing kernels and leaves. We obtained two additional alleles, flo4-2 and flo4-3, that also showed the same white-core endosperm phenotype. The flo4 kernels weighed about 6% less than wild-type ones. Starch contents in both kernel types were similar, but the total protein content was slightly higher in the mutant kernels. Moreover, lipid contents were significantly increased in the flo4 kernels. Expression analyses demonstrated that the cytosolic mRNA of OsPPDKB was induced in the reproductive organs after pollination, and greatly increased until about 10 days after fertilization. This mRNA was localized mainly in the endosperm, aleurone, and scutellum of the developing kernel. Our results suggest that cytosolic PPDK functions in rice to modulate carbon metabolism during grain filling.