A Combined Proteome and Transcriptome Analysis of Developing Medicago truncatula Seeds

Abstract

A comparative study of proteome and transcriptome changes during Medicago truncatula (cultivar Jemalong) seed development has been carried out. Transcript and protein profiles were parallel across the time course for 50% of the comparisons made, but divergent patterns were also observed, indicative of post-transcriptional events. These data, combined with the analysis of transcript and protein distribution in the isolated seed coat, endosperm, and embryo, demonstrated the major contribution made to the embryo by the surrounding tissues. First, a remarkable compartmentalization of enzymes involved in methionine biosynthesis between the seed tissues was revealed that may regulate the availability of sulfur-containing amino acids for embryo protein synthesis during seed filling. This intertissue compartmentalization, which was also apparent for enzymes of sulfur assimilation, is relevant to strategies for modifying the nutritional value of legume seeds. Second, decreasing levels during seed filling of seed coat and endosperm metabolic enzymes, including essential steps in Met metabolism, are indicative of a metabolic shift from a highly active to a quiescent state as the embryo assimilates nutrients. Third, a concomitant persistence of several proteases in seed coat and endosperm highlighted the importance of proteolysis in these tissues as a supplementary source of amino acids for protein synthesis in the embryo. Finally, the data revealed the sites of expression within the seed of a large number of transporters implied in nutrient import and intraseed translocations. Several of these, including a sulfate transporter, were preferentially expressed in seeds compared with other plant organs. These findings provide new directions for genetic improvement of grain legumes. A comparative study of proteome and transcriptome changes during Medicago truncatula (cultivar Jemalong) seed development has been carried out. Transcript and protein profiles were parallel across the time course for 50% of the comparisons made, but divergent patterns were also observed, indicative of post-transcriptional events. These data, combined with the analysis of transcript and protein distribution in the isolated seed coat, endosperm, and embryo, demonstrated the major contribution made to the embryo by the surrounding tissues. First, a remarkable compartmentalization of enzymes involved in methionine biosynthesis between the seed tissues was revealed that may regulate the availability of sulfur-containing amino acids for embryo protein synthesis during seed filling. This intertissue compartmentalization, which was also apparent for enzymes of sulfur assimilation, is relevant to strategies for modifying the nutritional value of legume seeds. Second, decreasing levels during seed filling of seed coat and endosperm metabolic enzymes, including essential steps in Met metabolism, are indicative of a metabolic shift from a highly active to a quiescent state as the embryo assimilates nutrients. Third, a concomitant persistence of several proteases in seed coat and endosperm highlighted the importance of proteolysis in these tissues as a supplementary source of amino acids for protein synthesis in the embryo. Finally, the data revealed the sites of expression within the seed of a large number of transporters implied in nutrient import and intraseed translocations. Several of these, including a sulfate transporter, were preferentially expressed in seeds compared with other plant organs. These findings provide new directions for genetic improvement of grain legumes. Seed development starts with the formation of a protective seed coat, the testa, derived from the maternal ovule integuments, which enclose the the endosperm, and embryo. These tissues are in as by the that the maternal of seed coat and the of endosperm are to seed in of and of endosperm are to seed in these tissues are in the endosperm embryo, the is and metabolic to a quiescent state of and metabolic and during the from to truncatula seeds. seed were to the of seed to and and is and for seed seed the seed coat synthesis in the tissues by from the and of legume seed sulfur in the of truncatula of the for seed and also seed a major in sulfur and is by a of in to the of sulfur in the and of the seeds of the the endosperm as the major in but with a protein of the of grain is the with protein from to as as and the seed has endosperm the major of and the of legume seeds are in and in the sulfur-containing amino acids and methionine of the that the amino of the protein in seeds is of also nutrient availability during seed filling protein and of the synthesis of a protein in legume and seeds are major and and are nutritional transcriptome and proteome of seeds of truncatula seed development the time of metabolic to and time course truncatula with expression in and A study of seed filling in of expression and proteome of expression during seed and of the seed proteome during development and analysis of the transcriptome expressed analysis of expression during of the during seed development in analysis of endosperm proteome a for in changes in expression during seed new strategies are by transcript and protein protein by transcript from that comparisons been for and and comparative analysis of the proteome and transcriptome of proteome analysis in for and analysis of the with proteome analysis and and with transcriptome proteome and transcriptome analysis of of from analysis of and and are also in expressed is as of of and to metabolic was to a comparative study of the proteome and transcriptome and levels during seed to the Medicago a legume by a of seed development to that of other the a of endosperm between and legume and of the seeds 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This the formation of sulfate from which in the is by the of to a sulfur for the synthesis of including and in the is to provide for by and enzymes involved in and are expressed in the seed coat and the embryo, the and are expressed within the seed coat and the These findings that sulfate in the tissues surrounding the embryo is and of the sulfate the embryo is for the synthesis of This compartmentalization, with that for the Met may a of the embryo in of during seed filling of these metabolic new directions for genetic improvement of grain in the essential amino to value for and the metabolic the to seed filling is protein in the seed coat and endosperm, which amino acids for the embryo. has been that seeds in in the of are to embryo by from the embryo surrounding tissues of truncatula embryo development to that in isolated are Several expressed preferentially in the endosperm and in the seed coat and are for in of and and in the and of the with and of a proteases from transcript and protein in the and were in other tissues a seed from the of seed filling and a endosperm were in in in the endosperm and in seed coat are by and protein patterns during seed that may in the between transcript and protein levels that the of proteases in seeds is by transcript of expression of the seed is to that of a expressed in the in are of plant seed expression of a from A is for formation in and and a in is of between seed a for the transcriptome study revealed transporters involved in the of in within the seed of were preferentially expressed in the embryo surrounding tissues and are involved in the of from the in the of to the embryo. the amino were preferentially expressed in seed coat endosperm, as the seed amino transcript a protein with to the to the of in for to regulate in and of analysis of and This was preferentially expressed in seed coat and endosperm and a to the of for sulfate transporters preferentially expressed in the embryo and in the seed coat and is preferentially expressed in seeds compared with other plant and levels during the protein to the which sulfate in the of and contribution of sulfate and import to seed sulfur to the between and protein patterns from of seed filling to study has revealed a of the and maternal in Met and sulfur This may by the genetic of maternal but also by the and of the tissues. of the in of and availability of a for in in which may and a to active during of legume seed of expression during seed seeds of is by in levels within the of the embryo Several from and and and were in the truncatula embryo and that also and the state the to regulate